UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
Form 6-K
Report of Foreign Private Issuer
Pursuant to Rule 13a-16 or 15d-16
Of the Securities Exchange Act of 1934
For the month of December 2024
Commission File Number: 001-38164
CALEDONIA MINING CORPORATION PLC
(Translation of registrant's name into English)
B006 Millais House
Castle Quay
St Helier
Jersey JE2 3EF
(Address of principal executive office)
Indicate by check mark whether the registrant files or will file annual reports
under cover of Form 20-F or Form 40-F.
Form 20-F [ X ] Form 40-F [ ]
INCORPORATION BY REFERENCE
The information contained in the section "Information Contained in this Report on Form 6-K"
shall be deemed to be incorporated by reference in the Registration Statement on Form F-3 of Caledonia Mining Corporation Plc (File No. 333-281436) of the Company, as amended or supplemented, to the extent not superseded by documents
or reports subsequently filed.
Exhibits 99.1, 99.2 and 99.3 included with this report are expressly incorporated
by reference into this report and are hereby incorporated by reference as exhibits to the Registration Statement on Form F-3 of Caledonia Mining Corporation Plc (File No. 333-281436), as amended or supplemented.
INFORMATION CONTAINED IN THIS REPORT ON FORM 6-K
New S-K 1300 Technical Report Study for the Bilboes Gold Project
Caledonia Mining Corporation Plc (Caledonia) announces the publication
of a new Technical Report Summary (TRS) titled “Bilboes Gold Project Technical Report Summary” on the Bilboes Gold Project,
Zimbabwe (Bilboes or the Project), prepared by DRA Projects (Pty) Ltd (DRA) in accordance with Subpart 1300 and Item 601(b)(96) of Regulation
S-K, as adopted by the United States Securities and Exchange Commission (S-K 1300), with an effective date of May 30, 2024. The results
of the TRS are summarized below.
Report Purpose
Caledonia mandated DRA to complete the TRS to report an Initial Assessment
(IA) on the Bilboes Gold Project, Zimbabwe. The purpose of the TRS is to report mineral resources in accordance with S-K 1300, to present
the results of an IA for the implementation of open pit mining to recover the gold mineralization and to propose additional work required
for feasibility level studies.
Project Location
The Bilboes properties are located in the Matabeleland North Province of
Zimbabwe. The Isabella-McCays properties are situated approximately 80 km north of Bulawayo while Bubi is situated approximately 100 km
north of Bulawayo. Bubi is 32 km due north-east of Isabella.
Bilboes have rights to three groups of claims covering an area of 2,731.6
ha that consist of four open-pit mining properties in Matabeleland North Province of Zimbabwe. These open pits are referred to as Isabela
North; Isabela South; McCays and Bubi in the figure below.
History
Initial exploration allowed the estimation of a small oxide Resource and
an open-pit; heap-leach mine was commissioned in 1989. Some 95,877 oz of was produced since 2003. Subsequent exploration extended Isabella
and new discoveries were made at Bubi and McCays, which has yielded production of 9,136 kg of gold (293,729 oz) to December 2023. All
mining has been from open pit oxide ore utilizing the heap leach extraction processing method.
Pilot Plant Test Work
The pilot plant test work was conducted over a period of six months from
April 2018 to September 2018, utilizing 20 t of the Isabella McCays ore and 15 t of Bubi ore. The Isabella McCays ores gold recoveries
ranged from 85.9% to 91.0% and the mass pulls ranged from 3.8% to 6.0% with a weighted average of 88.4% recovery and 5.0% mass pull. The
Bubi ore recoveries ranged from 85.9% to 88.8% and mass pulls ranged from 7.8% to 15.2% with averages of 87.5% recovery and 10.0% mass
pull.
Mineral Resource Estimate
The TRS declared a mineral resource estimate (MRE) in terms of S-K 1300,
which is summarized in the table below using a cut-off grade of 0.9 g/t Au and constrained inside a Lerchs-Grossman (LG) optimized pit
shell using US$ 2,400 per ounce gold price.
Mineral Resource based on a 0.9g/t Au Cut-Off Grade
Mineral Resources (0.9 g/t Au) Reference Point : In Situ |
Property |
Classification |
Tonnes (Mt) |
Au (g/t) |
Metal (kg) |
Ounces (koz) |
Isabella South (ISBS) |
Measured |
1.325 |
2.34 |
3,104 |
100 |
Indicated |
5.211 |
2.17 |
11,299 |
363 |
Total Measured and Indicated |
6.537 |
2.20 |
14,403 |
463 |
Inferred |
1.335 |
1.80 |
2,404 |
77 |
Isabella North (ISBN) |
Measured |
2.589 |
2.68 |
6,939 |
223 |
Indicated |
4.430 |
2.31 |
10,246 |
329 |
Total Measured and Indicated |
7.019 |
2.45 |
17,186 |
553 |
Inferred |
1.613 |
2.18 |
3,520 |
113 |
Bubi |
Measured |
1.288 |
1.95 |
2,518 |
81 |
Indicated |
14.006 |
2.19 |
30,708 |
987 |
Total Measured and Indicated |
15.294 |
2.17 |
33,225 |
1,068 |
Inferred |
5.116 |
1.8 |
9,208 |
296 |
McCays |
Measured |
0.925 |
3.05 |
2,821 |
91 |
Indicated |
3.874 |
2.37 |
9,193 |
296 |
Total Measured and Indicated |
4.799 |
2.50 |
12,014 |
386 |
Inferred |
1.054 |
2.16 |
2,274 |
73 |
Totals (ISBS +ISBN+ Bubi + McCays) |
Total Measured |
6.128 |
2.51 |
15,382 |
495 |
Total Indicated |
27.522 |
2.26 |
61,446 |
1,976 |
Total Measured and Indicated |
33.650 |
2.30 |
76,828 |
2,470 |
Total Inferred |
9.118 |
1.99 |
17,406 |
560 |
S-K 1300 definitions observed for classification
of mineral resources.
Mineral resources are reported in-situ.
Resources are constrained by a Lerchs-Grossman
(LG) optimized pit shell using Whittle software.
Mineral resources are not mineral reserves and have no demonstrated
economic viability. The estimate of mineral resources may be materially affected by mining, processing, metallurgical, infrastructure,
economic, marketing, legal, environmental, social, and governmental factors (Modifying Factors).
An IA is preliminary in nature, it includes inferred mineral resources that are
considered too speculative geologically to have the economic considerations applied to them that would enable them to be categorized as
mineral reserves, and there is no certainty that the IA will be realized.
Numbers may not add due to rounding.
The MRE has been depleted to reflect mining
up to 31 December 2023
Effective Date of resource estimate is
31 December 2023.
Mineral Reserve
The TRS did not declare mineral reserves.
Mining Methods
The Bilboes Gold Project consists of four mining areas containing between
one to three pits each. These areas are labelled as McCays, Isabella South, Isabella North and Bubi in the figure below.
Block Plan Showing Bilboes Pits and Process Plant Location
Based on the analysis of the engineering geological aspects of the investigated
deposits which included rock mass characterization, hydrogeology, intact rock properties and structural geology, a geotechnical model
comprising design parameters was developed. Using these design parameters; kinematic, empirical and limit equilibrium analysis was conducted
to determine the optimal slope configuration for the various deposits.
Based on the analysis conducted, it is understood that the capacity of
the slopes should be affected by the following:
| · | Completely weathered slopes should be a maximum of 3 m in height, and it is recommended that the material
is pushed back from the crest, |
| · | For the transitional rock (highly to moderately weathered), by a combination of rock mass strength and
adverse structural orientation. Inter-ramp heights of 60 m are achievable with inter-ramp angles between 45°and 50°, |
| · | For the unweathered rock slopes adverse structural orientation should determine the slope angle which
is achievable. Inter-ramp heights of 90 m are achievable with inter-ramp angles of between 50° and 55°, depending on the wall
direction. |
In the IA the previous Base Case was revalidated with Phase 1 being a 240
ktpm gold processing plant treating run of mine (RoM) material from Isabella and McCays (after a short ramp-up period) before being upgraded
for a Phase 2 to treat RoM material from the Bubi pit at 180 ktpm.
The inputs to the whittle optimization include revenue related financial
parameters, geotechnical parameters, various waste mining costs and the process plant throughput.
Dilution of 4% and mining losses of 5% loss were assumed.
The life of mine (LoM) schedule considers the blending requirement that
a maximum of 50% of feed to plant be sourced from Isabella North and the remainder from Isabella South (preferred blend) or McCays. Irregular
waste production profiles were smoothed to ensure the production profile is practically implementable.
Recovery Methods
Plant feed will be derived from two main mining areas, namely Isabella
McCays and Bubi, with production throughput to be phased over LoM as described in each scenario.
Operations in the process plant can essentially be divided into the following
sections:
| · | Comminution (plant feed size reduction by crushing and milling to facilitate liberation of the mineral
particles for subsequent downstream concentration), |
| · | Flotation (concentration of sulfides and gold into a small concentrate mass), |
| · | Biological oxidation (BIOX®) (destruction of the sulfides in the concentrate using oxidizing bacteria
to expose the gold particles for downstream recovery), |
| · | Carbon in leach (cyanidation leach of the BIOX® residue and recovery of the solubilized gold onto
activated carbon), |
| · | Electrowinning and smelting, |
The unit operations will be appliable to all three scenarios described
in the IA report. Further detail covering the test work and processing route can be found in the historical feasibility study reports.
A simplified schematic flow diagram is presented below.
Simplified Process Flow Diagram Tailings Storage Facility
SLR Consulting (Africa) (Pty) Ltd (SLR) were engaged to optimize the tailings
storage facility (TSF) as a follow on to investigate a new concept design and associated costing based on a phased paddock approach for
base case. The objectives were to minimize initial capital outlay and delay further expenditure according to a three-phase build programme
that aligned with the LoM production schedule.
Project Infrastructure
The overall site plan below includes major facilities of the Project including
the Isabella North and South, McCays and Bubi open pit mines, gold processing plan, TSF, waste stockpiles, demarcated areas for mine buildings
and accommodation facilities, main power line internal mine roads and access public roads.
Grid power will be supplied from the Zimbabwe National Grid by constructing
a 70 km 132 kV
Lynx line from Shangani Substation. To feed the line, a line bay will be
constructed at Shangani. A mine substation will be constructed at Isabella.
The estimate received is for a 132kV substation, equipped with a 50 MVA
132/33 kV step-down transformer. Raw water will be provided from open pit dewatering and the wellfield boreholes located across the mine
license area.
Overall Site Plan
Social and Community Related Requirements and Plans
An Environmental and Social Management Plan has been developed which contains
the environmental, social and safety management and monitoring commitments that Bilboes will implement to manage the negative impacts
and enhance the positive impacts identified in the Environmental Impact Assessment study. This will include:
| · | A Livelihoods Restoration Plan (LRP), |
| · | Several Corporate Social Responsibility (CSR) programmes, |
| · | Develop a fair and transparent labor, working conditions and recruitment policy, |
| · | A local procurement policy will be developed and implemented, |
| · | Develop a Stakeholder Engagement Plan, |
| · | Addressing the social or community impacts. |
Capital Costs
DRA has developed and costed two distinct project phases:
| · | Phase 1: Processing 240 ktpm of milled plant feed from the Isabella McCays mining area, scheduled for
years 1 to 6, |
| · | Phase 2: Processing 180 ktpm of milled plant feed from the Bubi mining area, scheduled for years 6 to
10. |
The estimate assumes that the project will be executed on an Engineering,
Procurement, and Construction Management basis.
The mining costs are a combination of site establishment and pre-development
during the production ramp up which consists of the first nine months of production.
The capital estimate is summarized in the table below.
Capital Summary per Project Phase
Description |
Grand Total |
Sub Total Phase 1 (Million US$) |
Sub Total Phase 2 (Million US$) |
(Million US$) |
Mining |
25.54 |
25.54 |
0.00 |
Process and Infrastructure |
311.82 |
267.63 |
44.19 |
Indirect Costs |
31.79 |
29.57 |
2.21 |
Contingency |
33.82 |
29.49 |
4.33 |
Total Project Costs |
402.97 |
352.24 |
50.73 |
Operating Costs
The operating cost estimate has been completed from a zero base and presented
in United States Dollar (US$). Costs associated with labor, materials and consumables have been included in this estimate.
Mining Contractor Costing
The average mining cost based on pricing received is US$ 2.65 /t including
the plant feed transport cost from all mining areas process plant. The cost breakdown is shown in the table below.
Mining Contractor OPEX
Area |
Cost per Total Tonne Mined (Ore and Waste) (US$)
|
G&A |
0.29 |
Drill and Blast |
0.45 |
Load and Haul Incl. Rehandle and Services |
1.91 |
Total |
2.65 |
Diesel Cost |
1.52 (October 2023) |
Process Plant Operating Cost
Operating costs have been estimated and based on the production profile
for LoM. Steady state costs are presented for Phase 1 and Phase 2 in the table below. Main drivers in costs include reagents and power
which collectively account for more than 70% of total plant operating costs.
Plant OPEX
Description |
Unit |
Phase 1: 240 ktpm IM |
Phase 2: 180 ktpm Bubi |
Variable |
US$ m/a |
37.93 |
53.33 |
Fixed |
US$ m/a |
12.31 |
17.17 |
Overview |
|
|
|
RoM |
t/a |
2,880,000 |
2,160,000 |
Total variable |
US$ m/a |
37.93 |
53.33 |
Total fixed |
US$ m/a |
12.31 |
17.17 |
Total |
US$ m/a |
50.24 |
70.49 |
Unit cost |
US$/t RoM |
17.44 |
32.64 |
General and Administration Cost
The general and administration cost (G&A) cost includes administrative
personnel, general office supplies, safety and training, travel (both on site and off site), independent contractors, insurance, permits,
fuel levies, security, camp power, camp costs, ICT, relocation, and recruitment.
Total G&A costs amount to US$ 4,912,650 per annum in phases 1 and 2.
Total Operating Costs Summary
The Bilboes total operating costs have been estimated and based on the
production profile over LoM.
LoM Operating Cost Summary
Description |
Cost (US$ m) |
Unit cost (US$ / t RoM) |
Mining |
596.13 |
25.54 |
Process Plant |
564.31 |
24.18 |
G&A |
47.17 |
2.02 |
Total |
1,207.61 |
51.74 |
Market Studies
The Gold Trade Act empowers the Minister responsible for Finance to issue
a Gold Dealers License which entitles entities to export and sell gold from Zimbabwe to customers of their choice. Prior to 1 June 2021,
only Fidelity Gold Refinery (Private) Limited (FGR) had the Gold Dealership License and therefore all gold bullion was sold to FGR. With
effect from 1 August 2021, all gold producers can directly sell any incremental production to customers of their choice using FGR’s
license to export. Caledonia’s Blanket Mine is currently selling 75% of its gold to a customer of its choice outside Zimbabwe by
exporting the gold using FGR’s license.
Sales proceeds from the exported gold are received directly into Blanket's
bank account in Zimbabwe. As all Bilboes production is considered incremental, Bilboes will be able to sell its gold directly to customers
of its choice or to continue selling to FGR.
Bilboes is confident that it will be able to export and sell its gold production
on similar terms as those currently in place between FGR and Blanket.
Economic Outcomes
The financial model has been prepared on a 100% equity project basis and
does not consider alternative financing scenarios. A discount rate of 10% has been applied in the analysis. The outcomes are presented
on a pre-tax and post-tax basis.
A static metal price of US$ 1,884/oz has been applied, based on a three-year
trailing average price up to April 2024. All-in sustaining costs have been reported as per the World Gold Council guideline dated November
2018 and are exclusive of project capital, depreciation, and amortization costs. Capital payback is exclusive of the construction period
and referenced to the start of first production.
Project Economics Summary
Description |
Units |
Values |
Financial Outcomes (Post-tax, Constant Model Terms) |
|
|
NPV @ 10% |
US$ m |
308.73 |
IRR |
% |
33.99 |
Peak Cash Funding |
US$ m |
309.18 |
AISC |
US$/oz |
967.90 |
Payback (UNDISCOUNTED) - From Production Start |
years |
1.9 |
A data table analysis has been conducted to specifically illustrate the
influence of changes in gold pricing and discount rates on the project's economic outcomes and is presented (bold) in the table below
that indicates the current base case scenario. The NPV and payback period (undiscounted, from production start) are presented on a post-tax
basis.
Data Table Analysis
|
Discount Rate (%) |
|
Gold Price
(USD/oz) |
15% |
12.5% |
10% |
7.5% |
5% |
Payback Period (Post-tax), years |
NPV (Post-tax), USD M |
1,500 |
31 |
59 |
94 |
137 |
191 |
3.6 years |
1,700 |
116 |
157 |
206 |
267 |
342 |
2.5 years |
1,884 |
194 |
246 |
309 |
385 |
480 |
1.9 years |
2,000 |
243 |
302 |
373 |
460 |
567 |
1.8 years |
2,200 |
327 |
398 |
484 |
588 |
717 |
1.6 years |
2,400 |
411 |
494 |
594 |
717 |
867 |
1.5 years |
2,600 |
495 |
590 |
705 |
845 |
1016 |
1.3 years |
Conclusions of DRA as the Qualified Person
Mineral Resource Estimate
| · | The data collected during the exploration, drilling and sampling programmes, including surveying, drill
hole logging, sampling, geochemical analysis, and data quality assurance, was collected in a professional manner and in accordance with
appropriate industry standards by suitably qualified and experienced personnel. |
| · | The geological modelling and mineral resource estimate were undertaken utilizing recognized deposit and
industry strategies/methodologies for the type of deposit of the Bilboes mine. |
| · | The mineral resource is constrained in an optimized pit shell. This together with the assumptions relating
to mining, processing, infrastructure, and market factors supports the “reasonable prospects for eventual economic extraction”. |
| · | Based on an assessment including data quality and integrity, data spacing, confidence in the grade interpolation,
confidence in the geological interpretation and confidence in the estimate DRA believes the mineral resource estimate is robust. |
Mining Engineering
| · | Both the modelling and the grade interpolation have been conducted in an unbiased manner and the resulting
grade and tonnage estimates should be reliable within the context of the classification applied. |
| · | The open pit modelling is based on suitably supported assumptions and parameters and completed utilizing
appropriate industry standards suitable for the Bilboes Project. |
| · | The economic modelling is supported by technical studies in mining, processing, infrastructure, environmental,
social, and marketing. Based on the inputs from these disciplines, the financial model demonstrates an economically viable mine. The economic
analysis is based on a gold price of US$ 1,884/oz. |
| · | The sensitivity analyses demonstrates that the profitability of the project is most sensitive to revenue
related factors such as gold price and recovery. |
Recommendations of DRA as the Qualified Person
| · | Based on the study work completed it shows an attractive economic outcome. It is recommended that the
Bilboes Project enters into a feasibility study phase. This is estimated by DRA to cost $ 1,429,000. |
SIGNATURES
Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly
caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.
|
CALEDONIA MINING CORPORATION PLC |
|
(Registrant) |
|
|
|
|
Date: December 16, 2024 |
/s/ JOHN MARK LEARMONTH |
|
John Mark Learmonth |
|
CEO and Director |
|
|
EXHIBIT INDEX
Exhibit 99.1
| // | |
DATE AND SIGNATURE PAGE
This technical report summary titled “Bilboes Gold Project Technical
Report Summary” was prepared for Caledonia Mining Corporation Plc, in accordance with Subpart 1300 and Item 601(b)(96) of Regulation
S-K, as adopted by the United States Securities and Exchange Commission. Its effective date is 30 May 2024.
The Qualified Person (“QP”)
responsible for this Report is:
DRA Projects (Pty) Ltd
Name: Tertius van Niekerk
Title: Senior Vice President Mining
DRA Projects (Pty) Ltd
Name: Alistair Hodgkinson
Title: Chief Operating Officer
| // | |
ABBREVIATIONS, TERMS AND DEFINITIONS
Abbreviations/Terms |
Definition |
°C |
Degrees |
AACE |
American Association of Cost Engineers |
AMIS |
African Mineral Standards |
amsl |
above mean sea level |
AMZIM |
Anglo American Corporation of Zimbabwe Ltd |
Archean |
Bubi Greenstone Belt |
Au |
Native Gold |
Baker Steel |
Baker Steel Resources Limited |
BBWi |
Bond Ball Work Index |
BFS |
Basic Ferric Sulphate |
Bilboes |
Bilboes Gold Limited |
BIOX |
Biological Oxidation |
BoQ |
Bill of Quantities |
Caledonia |
Caledonia Mining Corporation Plc |
CCD |
Counter Current Decantation |
CCE |
Capital Cost Estimate |
CIL |
Carbon in Leach |
CIM |
Canadian Institute of Mining |
CMCL |
AIM of the London Stock Exchange plc |
COS |
Crushed Ore Stockpile |
CRM’s |
Certified Reference Materials |
CSR |
Corporate Social Responsibility |
Datamine |
Datamine Studio™ |
DD |
Diamond Drilling |
DEM |
Digital Elevation Model |
DRA |
DRA Projects (Pty) Ltd |
ECandI |
Electrical, Control and Instrumentation |
EHS |
Environmental, Health and Safety |
EIA |
Environmental Impact Assessment |
EMA |
Environmental Management Agency |
EMC |
Eurus Mineral Consultants |
EMP |
Environmental Management Plans |
| // | |
Abbreviations/Terms |
Definition |
EPCM |
Engineering, Procurement, Construction Management |
EPO |
Exclusive Prospecting Orders |
ESIA |
Environmental and Social Impact Assessment |
ESMP |
Environmental and Social Management Plan |
ESSMS |
Environmental, Social and Safety Management System |
FEED |
Front End Engineering Design |
FGR |
Fidelity Gold Refinery |
GEV |
Generalized Extreme Value |
IA |
Initial Assessment |
IFC |
International Finance Commission |
ILO |
International Labor Organization |
IMTT |
Intermediated Money Transfer Tax |
Infinite Treasure |
Infinite Treasure Limited |
IRR |
Internal Rate of Return |
ISBN |
Isabella North |
ISBS |
Isabella South |
LBMA |
London Bullion Market Association |
LCR |
Lab Coarse Duplicates |
LG |
Lerchs-Grossman |
LoM |
Life of Mine |
LPR |
Lab Pulp Duplicates |
LRP |
Livelihoods Restoration Plan |
ma |
mega annum |
mamsl |
Meter above mean sea level |
MAP |
Mean Annual Precipitation |
MCC |
Motor Control Centre |
MEL |
Mechanical Equipment List |
MRE |
Mineral Resource Estimate |
MSD-Z |
Meteorological Services Department of Zimbabwe |
NPV |
Net Present Value |
OPEX |
Operating Expenditure |
P & G |
Preliminary and General |
PDC |
Process Design Criteria |
PERC |
percussion Reverse Circulation |
| // | |
Abbreviations/Terms |
Definition |
PFD |
Process Flow Diagram |
PFS |
Pre-Feasibility Study |
PGM |
Platinum Group Metals |
PLZ |
Performance Laboratories Zimbabwe Limited |
POX |
Pressure Oxidation |
PSD |
Particle Size Distribution |
PV |
Prospecting Ventures |
QA/QC |
Quality Assurance / Quality Control |
QP |
Qualified Person as defined in S-K 1300 |
RC |
Reverse Circulation |
RFQ |
Rock Quality Designation |
RMR |
Rock Mass Rating |
RoM |
Run of Mine |
RoR |
Rate of Rise |
RWD |
Return Water Dam |
SANAS |
South African National Accreditation System |
SEX |
Sodium Ethyl Xanthate |
SIB |
Stay in Business |
S-K 1300 |
Subpart 1300 and Item 601(b)(96) of Regulation S-K |
SLR |
SLR Consulting (Africa) (Pty) Ltd |
TRS |
Technical Report Summary within the meaning of S-K 1300 |
TSF |
Tailings Storage Facility |
US$ |
United States Dollar |
VAT |
Value Added Tax |
WGC |
World Gold Council |
WRD |
Waste Rock Dumps |
ZETDC |
Zimbabwe Electricity Transmission and Distribution Company |
ZINWA |
Zimbabwe National Water Authority |
SYSTEM OF UNITS
The international metric system of units (SI) will be used throughout the
design in all documentation, specifications, drawings, reports, and all other documents associated.
| // | |
1 EXECUTIVE SUMMARY |
19 |
1.1 Introduction |
19 |
1.2 Report Purpose |
19 |
1.3 Project Location |
19 |
1.4 Permits |
20 |
1.5 History |
20 |
1.6 Geology and Resource Estimate |
21 |
1.6.1 Geological
Setting and Mineralization |
21 |
1.6.2 Deposit
Types |
21 |
1.7 Exploration |
21 |
1.8 Sample Preparation, Analysis
and Security |
21 |
1.8.1 Data
Verification |
22 |
1.8.2 Metallurgical
Test Work |
22 |
1.8.3 Process
Route Identification |
23 |
1.8.4 Pilot
Plant Test Work |
24 |
1.8.5 BIOX® |
24 |
1.9 Mineral Resource Estimate |
25 |
1.10 Mineral Reserve |
27 |
1.11 Mining Methods |
27 |
1.12 Recovery Methods |
28 |
1.13 Project Infrastructure |
29 |
1.14 Environmental |
30 |
1.15 Project Permitting |
31 |
1.16 Social and Community Related
Requirements and Plans |
31 |
1.17 Mine Closure |
31 |
1.18 Capital Costs |
31 |
1.19 Operating Costs |
32 |
1.19.1 Mining
Contractor Costing |
32 |
1.19.2 Process
Plant Operating Cost |
33 |
1.19.3 General
and Administration Cost |
34 |
1.19.4 Total
Operating Costs Summary |
34 |
1.20 Market Studies |
34 |
1.21 Economic Outcomes |
35 |
1.22 Conclusions |
36 |
1.22.1 Mineral
Resource Estimate |
36 |
1.22.2 Mining
Engineering |
36 |
1.23 Recommendations |
37 |
| // | |
2 INTRODUCTION |
38 |
2.1 Report Purpose |
38 |
2.2 Sources of Information |
38 |
2.3 Personal Inspections /
Site Visits |
38 |
2.4 QP Responsibilities and
Relationships |
38 |
3 PROPERTY DESCRIPTION |
40 |
3.1 Project Location |
40 |
3.2 Property Area |
40 |
3.3 Mineral Tenure and Title |
41 |
3.4 Royalties and agreements |
43 |
3.5 Permits |
43 |
3.6 Political Risks |
44 |
3.7 Indigenization and Economic
Empowerment |
44 |
4 ACCESSIBILITY, CLIMATE,
LOCAL RESOURCES, INFRASTRUCTURE AND PHYSIOGRAPHY |
45 |
4.1 Access |
45 |
4.2 Physiography |
45 |
4.3 Climate |
45 |
4.4 Local Resources and Infrastructure |
45 |
4.5 Personnel |
46 |
4.6 Supplies |
46 |
5 HISTORY |
47 |
5.1 Holdings |
47 |
5.2 Historical Sulfide Mineral
Resource Estimates |
47 |
5.3 Production |
50 |
5.3.1 Oxide
Mineralization |
50 |
5.3.2 Production
Summary |
50 |
6 GEOLOGICAL SETTING, MINERALIZATION
AND DEPOSIT |
52 |
6.1 Regional Geology |
52 |
6.1.1 The
Archean |
52 |
6.1.2 The
Proterozoic |
52 |
6.1.3 The
Phanerozoic |
54 |
6.2 Regional Geology as it
Relates to the Bilboes Properties |
55 |
6.3 Stratigraphy |
57 |
6.4 Deposit Types |
57 |
7 EXPLORATION |
59 |
| // | |
7.1 Geological
Mapping |
59 |
7.2 Trenching |
60 |
7.3 Ground Geophysical Surveying |
60 |
7.4 Prospecting and Sampling |
60 |
7.5 Drilling |
61 |
7.5.1 Sulfide
Exploration |
61 |
7.5.2 Logging
and Sampling Procedure |
65 |
7.6 Hydrology and Hydrological
Drilling |
65 |
7.7 Geotechnical Drilling |
66 |
8 SAMPLE PREPARATION, ANALYSES
AND SECURITY |
67 |
8.1 Sampling |
67 |
8.2 Analysis |
67 |
8.3 Sample Security |
68 |
8.4 Quality Control |
68 |
8.4.1 Blanks |
68 |
8.4.2 Standards |
68 |
8.4.3 Duplicates |
69 |
8.4.4 Umpire
Labs |
69 |
8.5 QP Commentary |
69 |
9 DATA VERIFICATION |
70 |
9.1 Historical Data |
70 |
9.2 2017/2018 Drilling Campaign |
70 |
9.3 QP Commentary |
70 |
10 MINERAL PROCESSING AND
METALLURGICAL TESTING |
71 |
10.1 Test Work Programme Overview |
71 |
10.2 Discussion of the Results |
71 |
10.2.1 Chemical
Analyses |
71 |
10.2.2 Mineralogical
Characterization |
72 |
10.2.3 Comminution |
73 |
10.3 Process Route Identification |
73 |
10.3.1 Gravity
Tests |
73 |
10.3.2 Preliminary
Flotation |
73 |
10.3.3 Flotation
Optimization |
73 |
10.3.4 Gold
Dissolution from Flotation Concentrates |
73 |
10.4 Variability Testing |
74 |
10.5 Pilot Plant Test Work |
74 |
10.5.1 Pilot
Plant Operation and Flowsheets |
74 |
| // | |
10.6 Pilot Plant
Results |
75 |
10.6.1 Recoveries
and Mass Pulls |
75 |
10.6.2 Chemical
Analyses of Bulk Concentrates |
75 |
10.6.3 Additional
Laboratory Test Work and Simulation |
75 |
10.6.4 Flotation
Rate and Comparative Grind Tests |
75 |
10.6.5 Modelling
and Simulation |
76 |
10.6.6 Projected
Operational Gold Recovery |
77 |
10.6.7 Improvements
in Flotation Gold Recovery |
77 |
10.7 BIOX® |
77 |
10.7.1 Test
work |
77 |
10.8 QP Commentary |
79 |
11 MINERAL RESOURCE ESTIMATES |
80 |
11.1 Topography |
80 |
11.2 Geological Database |
80 |
11.3 Bulk Density |
80 |
11.4 Geological Model |
81 |
11.5 Weathering and Oxidation |
83 |
11.6 Compositing |
84 |
11.7 Variography |
84 |
11.8 Top Capping |
85 |
11.9 Grade Estimation |
85 |
11.9.1 Krige
Neighborhood Analysis |
85 |
11.9.2 Estimation
Method |
85 |
11.9.3 Block
Model Parameters |
87 |
11.10 Model Validations |
87 |
11.11 Reconciliation |
88 |
11.12 Resource Classification |
88 |
11.13 Declaration |
91 |
11.14 QP Commentary |
93 |
12 MINERAL RESERVE ESTIMATES |
93 |
13 MINING METHODS |
94 |
13.1 Hydrological and Geotechnical
Investigation |
94 |
13.1.1 Hydrogeology |
94 |
13.1.2 Conclusion
and Recommendations |
94 |
13.1.3 Major
Rock Domains |
94 |
13.2 Rock Mass Classification |
95 |
13.3 Geotechnical Conclusions
and Recommendations |
95 |
| // | |
13.4 Mining Pit
Locations |
96 |
13.5 Mining Strategy |
98 |
13.6 Whittle Optimization Input
Parameters |
98 |
13.6.1 Financial
Parameters |
98 |
13.6.2 Geotechnical
and General Parameters |
99 |
13.6.3 Waste
Rock Cost - Mining |
99 |
13.6.4 Process
Plant Throughput |
100 |
13.7 Plant Feed Dilution and
Plant Feed Loss |
100 |
13.8 Whittle Optimization Results |
101 |
13.9 Whittle Production Schedule
Results |
103 |
13.10 Sensitivity analysis |
103 |
13.10.1 Scenario
80 ktpm then 60 ktpm Bubi |
103 |
13.10.2 Scenario
80 ktpm then 160 ktpm then 120tpm Bubi |
104 |
13.11 Sensitivity Results |
105 |
13.12 Mining Contractor Production
Costs |
106 |
13.12.1 Production
Fleets Required |
106 |
13.12.2 Waste
Rock Dumps |
106 |
14 PROCESSING AND RECOVERY
METHODS |
108 |
14.1 Process Test work Results |
108 |
14.2 Process Flow Description |
109 |
14.2.1 Comminution |
110 |
14.2.2 Flotation |
111 |
14.2.3 Biological
Oxidation (BIOX®) |
111 |
14.2.4 Carbon
in Leach |
112 |
14.2.5 Carbon
Treatment |
113 |
14.2.6 Electrowinning
and Smelting |
113 |
14.2.7 Tailings
Handling |
114 |
14.3 Plant Water Requirements |
114 |
14.4 Reagent Services |
114 |
15 INFRASTRUCTURE |
117 |
15.1 Geotechnical Investigation
and Design |
118 |
15.1.1 Tailings
Storage Facility Site |
118 |
15.1.2 Process
Plant Site |
119 |
15.1.3 Waste
Rock Dump Sites |
119 |
15.2 Civil Engineering and
Earthworks |
119 |
15.3 Mechanical Engineering |
120 |
15.4 Electrical Power Supply
and Reticulation (including Communications) |
121 |
| // | |
15.4.1 Interconnection
to National Grid |
121 |
15.4.2 Power
Requirements |
121 |
15.4.3 Emergency
Power |
122 |
15.5 General Infrastructure |
122 |
15.6 Water Management Infrastructure |
122 |
15.6.1 Water
Balance |
122 |
15.6.2 Ground
Water |
123 |
15.7 Sewage Management |
124 |
15.8 Project Execution |
124 |
15.8.1 Execution
Strategy |
124 |
15.8.2 Engineering
and Design |
124 |
15.8.3 Construction
Philosophy |
124 |
15.8.4 Schedule |
124 |
15.9 Tailings Storage Facility |
124 |
15.9.1 Design
Standards |
125 |
15.9.2 Design
Criteria |
125 |
15.9.3 Tailings
Physical Characterization |
127 |
15.9.4 Liner
Selection |
127 |
15.9.5 Seepage
/ Leakage Quality |
128 |
15.9.6 Contaminant
Plume Modelling |
128 |
15.9.7 TSF
Infrastructure |
129 |
15.9.8 TSF
Hazard Classification |
129 |
15.9.9 TSF
Operation and Monitoring |
129 |
15.9.10 TSF
Closure Concept |
129 |
15.9.11 TSF
Optimization |
129 |
16 MARKET STUDIES |
134 |
16.1 Historical Supply and
Demand |
134 |
16.2 Gold Sales in Zimbabwe |
136 |
16.3 FGR Gold Price Predictions |
137 |
17 ENVIRONMENTAL STUDIES,
PERMITTING, AND PLANS, NEGOTIATIONS, OR AGREEMENTS WITH LOCAL INDIVIDUALS OR GROUPS |
139 |
17.1 Environmental Issues |
139 |
17.2 Waste, Tailings, Monitoring
and Water Management |
140 |
17.2.1 Tailings
Management and Disposal |
140 |
17.2.2 Waste
Rock Management and Disposal |
141 |
17.2.3 Non-Mineralized
Waste Management |
142 |
17.2.4 Site
Environmental Monitoring |
142 |
| // | |
17.3 Project Permitting |
143 |
17.4 Social and Community Related
Requirements and Plans |
143 |
17.5 Social / Community Issues |
144 |
17.6 Mine Closure |
144 |
17.7 Estimated Environmental
Costs for Closure |
146 |
18 CAPITAL AND OPERATING COSTS |
147 |
18.1 Capital Cost Estimate |
147 |
18.1.1 Basis
of Estimate - Mechanical |
147 |
18.1.2 Basis
of Estimate – Civils and Earthworks |
147 |
18.1.3 Basis
of Estimates – Mechanical Equipment |
148 |
18.1.4 Basis
of Estimates – Steelwork, Platework and Piping |
148 |
18.1.5 Basis
of Estimates – Electrical Control and Instrumentation |
149 |
18.1.6 Capital
Costs Summary |
150 |
18.2 Operating Cost Estimate |
150 |
18.2.1 Mining
Contractor Costing |
151 |
18.2.2 Process
Plant Operating Cost |
151 |
18.2.3 General
and Administration Costs |
154 |
19 ECONOMIC ANALYSIS |
156 |
19.1 Introduction |
156 |
19.2 Method |
156 |
19.3 Sources of Information |
156 |
19.4 Exchange Rates |
158 |
19.5 Production Profile |
158 |
19.6 Taxes, Levies and royalties |
158 |
19.7 Capital Expenditure and
Phasing |
162 |
19.8 Stay in Business Capital |
162 |
19.9 Operating Expenditure |
163 |
19.10 Gold Recovery |
163 |
19.11 Gold Pricing |
164 |
19.12 Salvage Value |
164 |
19.13 Working Capital |
164 |
19.14 Sunk and On-going Capital |
164 |
19.15 Reclamation and Closure |
164 |
19.16 Royalty Tax |
164 |
19.17 Corporate Income Tax |
165 |
19.18 Discount Rate |
165 |
19.19 Economic Outcomes |
165 |
19.20 Cash Flow Model |
167 |
| // | |
19.21 Sensitivity
Analysis |
168 |
20 ADJACENT PROPERTIES |
169 |
21 OTHER RELEVANT DATA AND
INFORMATION |
172 |
22 INTERPRETATION AND CONCLUSIONS |
173 |
22.1 Mineral Resource Estimate |
173 |
22.2 Mining Engineering |
173 |
22.3 Economic Outcomes |
173 |
22.4 Risk Assessment |
174 |
23 RECOMMENDATIONS |
177 |
24 REFERENCES |
178 |
25 RELIANCE ON INFORMATION
PROVIDED BY THE REGISTRANT |
179 |
| // | |
LIST OF TABLES
Table 1.1: Test work Program Outline |
23 |
Table 1.2: Mineral Resource based on a 0.9g/t Au
Cut-Off Grade |
26 |
Table 1.3: Capital Summary per Project Phase |
32 |
Table 1.4: Mining Contractor OPEX |
32 |
Table 1.5: Plant OPEX |
34 |
Table 1.6: LoM Operating Cost Summary |
34 |
Table 1.7: Project Economics Summary |
35 |
Table 1.8: Data Table Analysis |
36 |
Table 2.1: Summary of Site Visits and Personal
Inspections |
38 |
Table 3.1: Bilboes Claims |
41 |
Table 5.1: Sulfide Inferred Mineral Resources as
of 2009 |
47 |
Table 5.2: Sulfide Mineral Resources (31 March
2017) 0.0 g/t Au Cut-Off Grade |
49 |
Table 5.3: Sulfide Mineral Resources (31 March
2017) 0.9 g/t Au Cut-Off Grade |
49 |
Table 5.4: Production Data from Bilboes Mines to
31 December 2023 |
51 |
Table 7.1: History of Sulfide Project Core Drilling
1994 - 1999 |
63 |
Table 10.1: Test work Program Outline |
71 |
Table 10.2: Optimum Flotation Conditions |
73 |
Table 10.3: Comparative Pilot Plant Simulated Recoveries |
76 |
Table 10.4: Flotation Residence Times |
76 |
Table 10.5: Summary of the Test Work Pre-Feasibility
Results |
78 |
Table 11.1: Summary of Drill Holes |
80 |
Table 11.2: Summary of Density Measurement per
Resource Area |
81 |
Table 11.3: Summary of the Geological Parameters
for the Geological Models |
81 |
Table 11.4: Variogram Parameters used for Grade
Estimation |
84 |
Table 11.5: Summary of Search Parameters |
86 |
Table 11.6: Block Model Configuration |
87 |
Table 11.7: Checklist Criteria for Resource Classification |
89 |
Table 11.8: Optimization Parameters used for the
Lerchs-Grossmann Shells |
91 |
Table 11.9: Mineral Resource based on a 0.9g/t
Au Cut-Off Grade |
92 |
Table 13.1: Isabella – McCays – Bubi
– Predicted drawdown vs. time |
94 |
Table 13.2: Percentage Rock Types at Different
Mining Pits |
94 |
| // | |
Table 13.3: Slope Design |
96 |
Table 13.4: Whittle Optimization Input Parameters:
Financial Parameters |
98 |
Table 13.5: Whittle Optimization Input Parameters:
Geotechnical and General Parameters |
99 |
Table 13.6: Whittle Optimization Input Parameters:
Waste Mining Cost |
100 |
Table 13.7: Process Plant Throughput |
100 |
Table 13.8: Whittle Optimization Results |
102 |
Table 13.9: Sensitivity Results |
105 |
Table 13.10: Adjudicated Mining Contractor Cost |
106 |
Table 14.1: Process Plant Design Criteria |
108 |
Table 14.2: Process Plant Major Reagents / Commodities |
115 |
Table 15.1: Proposed Soil and Rock Properties for
Foundation Modelling on the TSF Site |
118 |
Table 15.2: Proposed Soil and Rock Properties for
Foundation Modelling on Process Plant Site |
119 |
Table 15.3: Substation Loading |
121 |
Table 15.4: Building Infrastructure |
122 |
Table 15.5: Production Profile |
126 |
Table 15.6: Liner System |
128 |
Table 16.1: Predicted Gold Price |
137 |
Table 17.1: Potential Environmental Impacts |
139 |
Table 18.1: Capital costs Summary by Discipline |
150 |
Table 18.2: Life of Mine Mining Contractor Operating
Cost Summary |
151 |
Table 18.3: Reagent Cost and Consumption for Isabella
McCay’s and Bubi |
152 |
Table 18.4: Process Plant OPEX – Power |
153 |
Table 18.5: Process Plant OPEX |
154 |
Table 18.6: General and Administrative Cost |
155 |
Table 19.1: Economic Analysis - Sources of information |
157 |
Table 19.2: Exchange Rates |
158 |
Table 19.3: Capital Gains Tax |
160 |
Table 19.4: Vat Collection |
161 |
Table 19.5: Initial Capital Cost – Constant
Terms (2023) |
162 |
Table 19.6: SIB Capital Cost (LoM) – Constant
Terms (2023) |
163 |
| // | |
Table 19.7: Operational Cost Estimate
(LoM) – Constant Terms (2023) |
163 |
Table 19.8: Gold Recovery per Mineralization Property |
164 |
Table 19.9: Summary of Economic Outcomes |
165 |
Table 19.10: Cashflow Model |
167 |
Table 19.11: Data Table Analysis |
169 |
Table 20.1: Historic Gold Production from Mines
around Isabella McCays and Bubi to 1980 |
171 |
Table 22.1: Project Economics Summary |
174 |
Table 25.1: Sections where information/data from
the Registrant has been relied upon |
179 |
| // | |
LIST OF FIGURES
Figure 1-1: Regional Location of the Bilboes Project |
20 |
|
|
Figure 1-2: Block Plan Showing Bilboes Pits and Process Plant Location |
27 |
|
|
Figure 1-3: Simplified Process Flow Diagram Tailings Storage Facility |
29 |
|
|
Figure 1-4: Overall Site Plan |
30 |
|
|
Figure 3-1: Regional Location of the Bilboes |
40 |
|
|
Figure 3-2: Isabella-McCays Mine Claims Map |
42 |
|
|
Figure 3-3: Bubi Mine Claims Map |
43 |
|
|
Figure 6-1: Greenstone Belts and known Gold Deposits in Zimbabwe |
52 |
|
|
Figure 6-2: NNE Trending Great Dyke Cutting Across the Zimbabwe Craton |
53 |
|
|
Figure 6-3: Geological Map showing the Zimbabwe Craton and Mobile Belts |
54 |
|
|
Figure 6-4: Sedimentary Basins of Zimbabwe |
55 |
|
|
Figure 6-5: Regional Geological Map showing Bilboes Properties |
56 |
|
|
Figure 6-6: Bilboes Site Stratigraphy |
57 |
|
|
Figure 6-7: Geological Cross Section through the Isabella and McCays
Deposit |
57 |
|
|
Figure 6-8: Geological Cross section through the Bubi Mine |
58 |
|
|
Figure 7-1: Map of the Surface Geology at Bubi |
59 |
|
|
Figure 7-2: Map of the Surface Geology at Isabella McCays |
60 |
|
|
Figure 7-3: Plans Showing the Drilling for the Various Areas |
64 |
|
|
Figure 10-1: Pilot Plant Campaign Flowsheets |
75 |
|
|
Figure 11-1: Section View showing Oxidation Profile at ISBS |
83 |
|
|
Figure 13-1: Block Plan Showing Bilboes Pits and Process Plant Location |
97 |
|
|
Figure 13-2: Block Plan Showing Bilboes Pits Location |
97 |
|
|
Figure 13-3: Base Case Production Schedule 240/180 ktpm - Plant Feed
Grade |
103 |
|
|
Figure 13-4: Base Case Production Schedule 240/180 ktpm - Gold Ounces |
103 |
|
|
Figure 14-1: Bilboes Simplified Process Flow Diagram |
110 |
|
|
Figure 15-1: Mine Layout |
117 |
|
|
Figure 15-2: Overall Site Plan |
117 |
|
|
Figure 15-3: Phasing of Flotation TSF Compartment – 240 ktpm |
131 |
|
|
Figure 16-1: Historical Gold Supply (2010 - 2023) |
134 |
|
|
Figure 16-2: Historical Gold Demand (2010 - 2023) |
135 |
|
|
Figure 16-3: Gold Price (2010 - 2023) |
136 |
|
|
| // | |
Figure 19-1 Sensitivity Analysis |
168 |
|
|
Figure 20-1: Adjacent Properties around Isabella McCays and Bubi |
170 |
| // | |
This technical report summary titled “Bilboes Gold Project
Technical Report Summary” was prepared for Caledonia Mining Corporation Plc, in accordance with Subpart 1300 and Item 601(b)(96)
of Regulation S-K, as adopted by the United States Securities and Exchange Commission. Its effective date is May 30, 2024.
This Technical Report Summary (TRS) has been prepared for Caledonia
Mining Corporation Plc (Caledonia) on the Bilboes Gold Project, Zimbabwe which Caledonia acquired with the acquisition of Bilboes Gold
Limited (Bilboes) on 6 January 2023. Caledonia is a Zimbabwean focused exploration, development, and mining corporation. Caledonia shares
are listed on the NYSE American LLC and depositary interests in the shares are traded on the AIM of the London Stock Exchange plc (symbol:
CMCL). Caledonia listed depositary receipts on the Victoria Falls Stock Exchange, a subsidiary of the Zimbabwe Stock Exchange, on December
2, 2021.
Caledonia mandated DRA Projects (Pty) Ltd (DRA) to complete
this TRS to report an Initial Assessment (IA) on the Bilboes Gold Project, Zimbabwe. The purpose of this report is to report Mineral Resources
in accordance with S-K 1300, to present the results of an IA for the implementation of open pit mining to recover the gold mineralization
and to propose additional work required for feasibility level studies.
The Bilboes properties are located in the Matabeleland North
Province of Zimbabwe. The Isabella-McCays properties are situated approximately 80 km north of Bulawayo while Bubi is situated approximately
100 km north of Bulawayo. Bubi is 32 km due north-east of Isabella.
Bilboes have rights to three groups of claims covering an area
of 2,731.6 ha that consist of four open-pit mining properties in Matabeleland North Province of Zimbabwe. These open pits are referred
to as Isabela North; Isabela South; McCays and Bubi (Figure 1.1).
| // | |
Figure 1-1: Regional Location of the
Bilboes Project
Bilboes has been operating in Matabeleland since 1989. It holds
the necessary mining permits and complies with the terms of the Mines and Minerals Act and allied regulations with respect to all of their
claims and in particular that all of the registration certificates are valid, and the protection certificates are up to date. Bilboes
thus requires no further permits to explore or produce from the current operational areas, but further permits will be required for the
proposed haul road between Bubi and Isabella plant.
Further exploration outside the current claims will require
approvals by the Environmental Management Agency (EMA) who may request an Environmental Impact Assessment (EIA) study.
Initial exploration allowed the estimation of a small oxide
Resource and an open-pit; heap-leach mine was commissioned in 1989. Some 95,877 oz of was produced since 2003. Subsequent exploration
extended Isabella and new discoveries were made at Bubi and McCays, which has yielded production of 9,136 kg of gold (293,729 oz) to December
2023. All mining has been from open pit oxide ore utilizing the heap leach extraction processing method.
Exploration for sulfide Mineral Resources began in 1994/95,
with 17,650 m of exploratory drilling being completed by 1999, covering a strike length of 3,440 m.
A maiden Mineral Resource estimate for the sulfide Mineral
Resources was completed by SRK in 2009, containing 4.75 Mt of Inferred Mineral Resources grading 3.49 g/t. This estimate used a 2.0 g/t
cut-off for delineation of the mineral Resource estimation domains.
| // | |
|
1.6 |
Geology and Resource Estimate |
|
1.6.1 |
Geological Setting and Mineralization |
The Bubi Greenstone Belt (Archean) which consists of volcanic
rocks of the Upper Bulawayan Group and capped by sedimentary sequences of the Shamvaian Group, all of which have been metamorphosed into
felsic and mafic schists, underlies the Bilboes Properties. Gold deposits are concentrated at the interface between these two groups,
where major structural breaks and splays provide pathways for hydrothermal vein mineralization.
Gold is associated with sulfides that is commonly found in
hydrothermal systems. These include pyrite and arsenopyrite as major components, but copper, lead, zinc, antimony, are also present in
some deposits. Common alteration associated with gold mineralization is silicification, with lesser sericite and chlorite alteration.
Mineralization is hydrothermal and consists of silicified stockworks
that host pyrite and arsenopyrite. The stockworks are characterized by a series of subparallel echelon zones. The gold is very finely
dispersed within the sulfides and is refractory. All the deposits are oxidized with the sulfide interface occurring between 6 m and 50
m below surface.
Soil sampling, trenching and geological mapping have been progressively
conducted since exploration and oxide mining commenced in 1982. Soil sampling was used to identify areas for trenching and mapping. Trenches
were sampled at 1 m to 2 m intervals. The assays were used to guide the interpretation and projection of oxide mineralization along strike
and at depth. The assays from trench sampling were not used in grade estimation.
Ground Magnetics and Induced Polarization geophysical surveys
have been conducted at Isabella, as part of the oxide ore exploration since 1996.
Drilling of the sulfides to provide data for the mineral resource
estimate was done in three phases totalling 93,400 m. The first phase by Anglo American Corporation was between 1994 and 1999 and the
second phase by Bilboes from 2011 to 2013. The latest drilling was from December 2017 to November 2018.
The third campaign focused on upgrading of the mineral resources
from the Inferred and Indicated to Indicated and Measured categories.
|
1.8 |
Sample Preparation, Analysis and Security |
During the drilling campaigns, all geological logging and sampling
was conducted in accordance with Bilboes standard operating procedures which were adopted by AMZIM and enhanced over time to keep up with
industry best practices.
Independent South African National Accreditation System (SANAS)
accredited laboratories were used in the analyses of samples.
Performance Laboratories Zimbabwe Limited (PLZ) in Harare was
selected as the primary laboratory. ZIMLABS and Antech Laboratories (Antech) in Zimbabwe were used for check analyses.
| // | |
Certified Reference Materials (CRMs), blanks, field duplicates,
coarse and pulp repeats were used for Quality Assurance Quality Control (QA/QC) purposes.
The QP has assessed the standard operating procedures together
with the results of the QA/QC program and are of the view that these are adequate for the purposes of reporting the Mineral Resources
contained herein.
Before commencement of the 2017/2018 drilling campaign in addition
to the Datamine™ software already in place Bilboes acquired Fusion database software for the capture: storage and management of
drill hole information. This software has built in data verification tools to minimize transcription errors. Bilboes standard operating
procedure involves a thorough audit by a senior geologist of each drillholes’ geology and sampling logs, from data logging through
to capturing into the database and QA/QC checks.
Each hardcopy log is audited and signed-off by a senior geologist
prior to being used in modelling and estimation.
DRA visited the site during drilling and performed various
checks to verify the integrity of the collar co-ordinates, logging and sampling procedures, and assay results and concluded that the data
collection was consistent with industry standards.
|
1.8.2 |
Metallurgical Test Work |
The metallurgical test work campaign was concluded in different
phases over a period extending from September 2013 to March 2019 and involved various laboratories and consultants as outlined in Table
1.1. The outcomes from the test work have been used to define the processing route, process design basis and gold recoveries.
| // | |
Table 1.1: Test work Program Outline
Phase |
Test
work Description |
Done
By |
Supervision
and Oversight |
Date |
1A |
Sample characterization detailing mineralogical
and chemical analysis |
Mintek, South Africa |
Bilboes, MMC and MDM Engineering |
September 13 to December 13 |
1B |
Comminution test work done on the two composites
namely Composite 1 (Bubi ore) and Composite 2 (combination of Diana, Calcite, Castile, Maria and McCays ores) |
Mintek, South Africa |
Bilboes, MMC and MDM Engineering |
January 14 to April 14 |
2 |
Selection of a process route covering gravity
amenability tests, flotation optimization and treatment of the sulfide flotation concentrates via POX, Bio-Oxidation and Ultra-fine grinding
followed by cyanidation |
Mintek and Suntech, South Africa |
Bilboes and MMC |
May 14 to September 14 |
3 |
Variability flotation
tests and bulk flotation concentrate production for additional BIOX® and gold leach tests |
Suntech and SGS, South Africa |
Bilboes, Minxcon and MMC |
October 15 to August 16 |
4A |
Laboratory and Pilot plant test work campaigns
on the different ore types to generate additional flotation kinetics and grind data, bulk concentrates for BIOX® pilot plants, flotation
design parameters and validate flowsheet |
MMC at the client's project site in Zimbabwe |
Bilboes and DRA |
April 18 to September 18 |
4B |
Review, modelling and simulation of laboratory
and pilot plant test results |
EMC, South Africa |
Bilboes, MMC and DRA |
October 18 to March 19 |
|
1.8.3 |
Process Route Identification |
Gravity amenability tests indicated poor gold recoveries and
varied from 14% to 22% at 0.5% mass pull. Initial milling and flotation results indicated high gold recoveries of 89 - 97% with high mass
pulls ranging 10 -15%, low concentrate grades of 12-20 g/t Au and unacceptable high levels of carbonates in the range of 7-13% which were
bound to negatively affect the down-stream gold recovery process. Gold Dissolution from Flotation Concentrates using Biological Oxidation
(BIOX®) provided 99% sulfide decomposition with 97% gold dissolution by cyanidation of the bio-residue.
| // | |
Based on the test work and consideration of environmental impacts
and risk minimization by adopting commercially established and proven processes, the process route identified for additional evaluation
was flotation, pre-treatment of the concentrate by BIOX® followed by cyanidation.
|
1.8.4 |
Pilot Plant Test Work |
The pilot plant test work was conducted over a period of six
months from April 2018 to September 2018, utilizing 20 t of the Isabella McCays ore and 15 t of Bubi ore. The Isabella McCays ores gold
recoveries ranged from 85.9% to 91.0% and the mass pulls ranged from 3.8% to 6.0% with a weighted average of 88.4% recovery and 5.0% mass
pull. The Bubi ore recoveries ranged from 85.9% to 88.8% and mass pulls ranged from 7.8% to 15.2% with averages of 87.5% recovery and
10.0% mass pull.
Test work was conducted during 2019 on Ore samples from Isabella
McCays and Bubi deposits to develop test work data to design a gold processing plant.
The BIOX® test work indicated the following:
|
· |
An average BIOX® sulfide oxidation of 90% was achieved at a 6.5-day retention time and a feed slurry solids
concentration of 20%, |
|
· |
This resulted in an average CIL gold dissolution of 95.7% on the BIOX® product solids, |
|
· |
The BAT tests completed on the Bubi concentrate sample achieved sulfide oxidation levels in the range 97 –
98% and yielded gold dissolutions in the range 92.3 to 96.8%. |
|
1.9 |
Mineral Resource Estimate |
The Mineral Resource Estimate (MRE) has been declared in terms
of S-K 1300 (Table 1.2).
The Mineral Resource Estimate is summarized in Table 1.2 using
a cut-off grade of 0.9 g/t Au and constrained inside a Lerchs-Grossman (LG) optimized pit shell using US$ 2,400 per ounce gold price.
Mineral Resources exclude Mineral Reserves.
| // | |
Table 1.2: Mineral Resource based on
a 0.9g/t Au Cut-Off Grade
Mineral
Resources (0.9 g/t Au) Reference Point: In Situ |
Property |
Classification |
Tonnes
(Mt) |
Au
(g/t) |
Metal
(kg) |
Ounces (koz) |
Isabella
South (ISBS) |
Measured
|
1.325 |
2.34 |
3,104 |
100 |
Indicated
|
5.211 |
2.17 |
11,299 |
363 |
Total Measured
and Indicated |
6.537 |
2.20 |
14,403 |
463 |
Inferred |
1.335 |
1.80 |
2,404 |
77 |
Isabella
North (ISBN) |
Measured
|
2.589 |
2.68 |
6,939 |
223 |
Indicated
|
4.430 |
2.31 |
10,246 |
329 |
Total Measured
and Indicated |
7.019 |
2.45 |
17,186 |
553 |
Inferred |
1.613 |
2.18 |
3,520 |
113 |
Bubi
|
Measured
|
1.288 |
1.95 |
2,518 |
81 |
Indicated
|
14.006 |
2.19 |
30,708 |
987 |
Total
Measured and Indicated |
15.294 |
2.17 |
33,225 |
1,068 |
Inferred
|
5.116 |
1.8 |
9,208 |
296 |
McCays
|
Measured
|
0.925 |
3.05 |
2,821 |
91 |
Indicated |
3.874 |
2.37 |
9,193 |
296 |
Total Measured
and Indicated |
4.799 |
2.50 |
12,014 |
386 |
Inferred |
1.054 |
2.16 |
2,274 |
73 |
Totals
(ISBS +ISBN+ Bubi + McCays) |
Total
Measured |
6.128 |
2.51 |
15,382 |
495 |
Total Indicated
|
27.522 |
2.26 |
61,446 |
1,976 |
Total Measured
and Indicated |
33.650 |
2.30 |
76,828 |
2,470 |
Total Inferred
|
9.118 |
1.99 |
17,406 |
560 |
S-K
1300 definitions observed for classification of Mineral Resources.
Mineral Resources are reported
in-situ.
Resources
are constrained by a Lerchs-Grossman (LG) optimized pit shell using Whittle software.
Mineral Resources are not
Mineral Reserves and have no demonstrated economic viability. The estimate of Mineral Resources may be materially affected by mining,
processing, metallurgical, infrastructure, economic, marketing, legal, environmental, social, and governmental factors (Modifying Factors).
An IA is preliminary in nature, it includes inferred mineral
resources that are considered too speculative geologically to have the economic considerations applied to them that would enable them
to be categorized as mineral reserves, and there is no certainty that the IA will be realized
Numbers
may not add due to rounding.
The
Mineral Resource Estimate has been depleted to reflect mining up to 31 December 2023
Effective
Date of Resource Estimate is 31 December 2023.
| // | |
No Mineral Reserve is declared.
The Bilboes Gold Project consists of four mining areas containing
between one to three pits each. These areas are McCays, Isabella South, Isabella North and Bubi (Figure 1-2).
Figure 1-2: Block Plan Showing Bilboes
Pits and Process Plant Location
Based on the analysis of the engineering geological aspects
of the investigated deposits which included rock mass characterization, hydrogeology, intact rock properties and structural geology, a
geotechnical model comprising design parameters was developed. Using these design parameters; kinematic, empirical and limit equilibrium
analysis was conducted to determine the optimal slope configuration for the various deposits.
Based on the analysis conducted, it is understood that the
capacity of the slopes should be affected by the following:
|
· |
Completely weathered slopes should be a maximum of 3 m in height, and it is recommended that the material
is pushed back from the crest, |
|
· |
For the transitional rock (highly to moderately weathered), by a combination of rock mass strength and adverse
structural orientation. Inter-ramp heights of 60 m are achievable with inter-ramp angles between 45°and 50°, |
|
· |
For the unweathered rock slopes adverse structural orientation should determine the slope angle which is achievable.
Inter-ramp heights of 90 m are achievable with inter-ramp angles of between 50° and 55°, depending on the wall direction. |
| // | |
In this IA the previous Base Case was revalidated with Phase
1 being a 240 ktpm gold processing plant treating Run of Mine (RoM) material from Isabella and McCays (after a short ramp-up period) before
being upgraded for a Phase 2 to treat RoM material from the Bubi pit at 180 ktpm.
The inputs to the whittle optimization include revenue related
financial parameters, geotechnical parameters, various waste mining costs and the process plant throughput.
Dilution of 4% and mining losses of 5% loss were assumed.
The Life of Mine (LoM) schedule considers the blending requirement
that a maximum of 50% of feed to plant be sourced from Isabella North and the remainder from Isabella South (preferred blend) or McCays.
Irregular waste production profiles were smoothed to ensure the production profile is practically implementable.
Plant feed will be derived from two main mining areas, namely
Isabella McCays and Bubi, with production throughput to be phased over LoM as described in each scenario.
Operations in the process plant can essentially be divided
into the following sections:
|
· |
Comminution (plant feed size reduction by crushing and milling to facilitate liberation of the mineral particles
for subsequent downstream concentration), |
|
· |
Flotation (concentration of sulfides and gold into a small concentrate mass), |
|
· |
Biological oxidation - BIOX® (destruction of the sulfides in the concentrate using oxidizing bacteria
to expose the gold particles for downstream recovery), |
|
· |
Carbon in leach (cyanidation leach of the BIOX® residue and recovery of the solubilized gold onto activated
carbon), |
|
· |
Electrowinning and smelting, |
The unit operations will be appliable to all three scenarios
described in this IA report. Further detail covering the test work and processing route can be found in the historical feasibility study
reports. A simplified schematic flow diagram is presented in Figure 1.3.
| // | |
Figure 1-3: Simplified Process Flow
Diagram Tailings Storage Facility
SLR Consulting (Africa) (Pty) Ltd (SLR) were engaged to optimize
the TSF as a follow on to investigate a new concept design and associated costing based on a phased paddock approach for Base Case. The
objectives were to minimize initial capital outlay and delay further expenditure according to a three-Phase build programme that aligned
with the LoM production schedule.
|
1.13 |
Project Infrastructure |
The overall site plan is shown in Figure 1-4 and includes major
facilities of the Project including the Isabella North and South, McCays and Bubi open pit mines, gold processing plan, TSF, Waste Stockpiles,
demarcated areas for mine buildings and accommodation facilities, main power line internal mine roads and access public roads.
Grid power will be supplied from the Zimbabwe National Grid
by constructing a 70 km 132 kV
Lynx line from Shangani Substation. To feed the line, a line
bay will be constructed at Shangani. A mine substation will be constructed at Isabella.
The estimate received is for a 132kV substation, equipped with
a 50 MVA 132/33 kV step-down transformer. Raw water will be provided from open pit dewatering and the wellfield boreholes located across
the mine license area.
| // | |
Figure 1-4: Overall Site Plan
The Environmental and Social Impact Assessment (ESIA) and accompanying
specialist studies were conducted in conformance with the relevant International Finance Corporation (IFC) Performance Standards and associated
guidelines and in compliance with the legal framework of Zimbabwe. The Environmental Impact Assessment (EIA) (SLR, 2019) identified the
following potential environmental impacts:
The EIA (SLR, 2019) concluded that the proposed project presents
several potential positive and negative impacts associated with the unmitigated scenario. With mitigation (in the residual impact scenario)
some of the identified potential impacts can be prevented and the remainder can be managed and mitigated to remain within acceptable environmental
limits so long as the mitigation set out in the Environmental and Social Management Plan (ESMP) is implemented and Bilboes develops, implements,
and annually reviews the Environmental, Social and Safety Management System (ESSMS). Positive impacts can be enhanced by developing and
implementing a Community Development Plan as set out in the ESMP.
Bilboes is committed to implementing the mitigation measures
within the ESMP together with the ESSMS which will be implemented as part of Bilboes on-going efforts to achieve continuous environmental
improvement. The management system will contain plans and procedures to help manage environmental aspects and impacts and help ensure
legal compliance. Requirements for post-closure monitoring to determine whether the mitigation and rehabilitation measures are effective
would be incorporated into a final Closure Plan to be compiled for the operations prior to the commencement of decommissioning.
| // | |
An approved EIA is required in terms of the Environmental Management
Act (Chapter 20:27) No. 13 of 2002 and the Mines and Minerals Act (Chapter 21:05) of 1996. The ESIA was undertaken for the project to
satisfy the requirement and an ESIA Report was completed and submitted to the Environmental Management Agency (EMA) within the first quarter
of 2020. Thereafter, public feedback meetings were held to disclose the findings of the ESIA Report to the identified stakeholders. A
record of this disclosure process was compiled and submitted to the EMA. An EIA certificate was issued to Bilboes for the project in February
2021 and was valid for two years. The EIA certificate was renewed for one year to March 2024 and now to March 2025. The EIA certificate
renewal process will continue annually for the duration of the operations, subject to conditions which include project update reports,
compliance with Environmental Management Plans (EMP) outlined in the ESIA Report and notification to EMA for any changes in the project
likely to alter the project as stipulated in the ESIA Report. Other project related licenses include air emissions (generators, smelter,
incinerator), explosives (purchase and storage), firearms, medicines control, public health (medical examination), water abstract, hazardous
substances (importation, transportation, storage and use) and solid waste disposal which are renewed quarterly or annually.
|
1.16 |
Social and Community Related Requirements and Plans |
An ESMP has been developed which contains the environmental,
social and safety management and monitoring commitments that Bilboes will implement to manage the negative impacts and enhance the positive
impacts identified in the EIA. This will include:
|
· |
A Livelihoods Restoration Plan (LRP), |
|
· |
Several Corporate Social Responsibility (CSR) programmes, |
|
· |
Develop a fair and transparent labor, working conditions and recruitment policy, |
|
· |
A local procurement policy will be developed and implemented, |
|
· |
Develop a Stakeholder Engagement Plan, |
|
· |
Addressing the social or community impacts. |
Generally accepted “good international practice”
mine closure methods were used as the basis for the conceptual closure plan, as well as for determining the unit rates for the various
closure components used in the LoM liability calculation. The mine closure methods also conform to the statutory requirements of Zimbabwe
EMA, who are the regulatory body.
DRA has developed and costed two distinct project phases:
|
· |
Phase 1: Processing 240 ktpm of milled plant feed from the Isabella McCays mining area, scheduled for years
1 to 6, |
|
· |
Phase 2: Processing 180 ktpm of milled plant feed from the Bubi mining area, scheduled for years 6 to 10. |
| // | |
The estimate assumes that the project will be executed on an
Engineering, Procurement, and Construction Management (EPCM) basis.
The mining costs are a combination of site establishment and
pre-development during the production ramp up which consists of the first nine months of production.
The capital estimate is summarized in Table 1.3.
Table 1.3: Capital Summary per Project
Phase
Description
|
Grand
Total |
Sub
Total Phase 1 (Million US$) |
Sub
Total Phase 2 (Million US$) |
(Million
US$) |
Mining
|
25.54 |
25.54 |
0.00 |
Process
and Infrastructure |
311.82 |
267.63 |
44.19 |
Indirect
Costs |
31.79 |
29.57 |
2.21 |
Contingency
|
33.82 |
29.49 |
4.33 |
Total
Project Costs |
402.97 |
352.24 |
50.73 |
The operating cost estimate has been completed from a zero
base and presented in United States Dollar (US$). Costs associated with labor, materials and consumables have been included in this estimate.
|
1.19.1 |
Mining Contractor Costing |
The average mining cost based on pricing received is US$ 2.65
/t including the plant feed transport cost from all mining areas process plant. The cost breakdown is shown in Table 1.4.
Table 1.4: Mining Contractor OPEX
Area
|
Cost per Total Tonne Mined (Ore and
Waste) (US$) |
G&A
|
0.29 |
Drill
and Blast |
0.45 |
Load
and Haul Incl. Rehandle and Services |
1.91 |
Total
|
2.65 |
Diesel
Cost |
1.52 (October 2023) |
| // | |
|
1.19.2 |
Process Plant Operating Cost |
Operating costs have been estimated and based on the production
profile for LoM. Steady state costs are presented for Phase 1 and Phase 2 in Table 1.5. Main drivers in costs include reagents and power
which collectively account for more than 70% of total plant operating costs.
| // | |
Table 1.5: Plant OPEX
Description |
Unit |
Phase
1: 240 ktpm IM |
Phase
2: 180 ktpm Bubi |
Variable
|
US$ m/a |
37.93 |
53.33 |
Fixed
|
US$
m/a |
12.31
|
17.17 |
Overview
|
|
|
|
RoM |
t/a |
2,880,000 |
2,160,000 |
Total variable
|
US$ m/a |
37.93 |
53.33 |
Total fixed
|
US$ m/a |
12.31 |
17.17 |
Total |
US$ m/a |
50.24 |
70.49 |
Unit cost
|
US$/t RoM
|
17.44 |
32.64 |
|
1.19.3 |
General and Administration Cost |
The General and Administration Cost (G&A) cost includes
administrative personnel, general office supplies, safety and training, travel (both on site and off site), independent contractors, insurance,
permits, fuel levies, security, camp power, camp costs, ICT, relocation, and recruitment.
Total G&A costs amount to US$ 4,912,650 per annum in phases
1 and 2.
|
1.19.4 |
Total Operating Costs Summary |
The Bilboes Mines total operating costs have been estimated
and based on the production profile over LoM. A summary of LoM operating costs is shown in Table 1.6.
Table 1.6: LoM Operating Cost Summary
Description |
Cost
(US$ m) |
Unit
cost (US$ / t RoM) |
Mining |
596.13 |
25.54 |
Process Plant
|
564.31 |
24.18 |
G&A |
47.17 |
2.02 |
Total
|
1,207.61
|
51.74 |
The Gold Trade Act empowers the Minister responsible for Finance
to issue a Gold Dealers License which entitles entities to export and sell gold from Zimbabwe to customers of their choice. Prior to 1
June 2021, only Fidelity Gold Refinery (Private) Limited (FGR) had the Gold Dealership License and therefore all gold bullion was sold
to FGR. With effect from 1 August 2021, all gold producers can directly sell any incremental production to customers of their choice using
FGR’s license to export. Caledonia’s Blanket Mine is currently selling 75% of its gold to a customer of its choice outside
Zimbabwe by exporting the gold using FGR’s license.
| // | |
Sales proceeds from the exported gold are received directly
into Blanket's bank account in Zimbabwe. As all Bilboes production is considered incremental, Bilboes will be able to sell its gold directly
to customers of its choice or to continue selling to FGR.
Bilboes is confident that it will be able to export and sell
its gold production on similar terms as those currently in place between FGR and Blanket.
The financial model has been prepared on a 100% equity project
basis and does not consider alternative financing scenarios. A discount rate of 10% has been applied in the analysis. The outcomes are
presented on a pre-tax and post-tax basis.
A static metal price of US$ 1,884/oz has been applied, based
on a three-year trailing average price up to April 2024. All-in sustaining costs have been reported as per the World Gold Council
WGC) guideline dated November 2018 and are exclusive of project capital, depreciation, and amortization costs. Capital payback is exclusive
of the construction period and referenced to the start of first production.
(Key financial outcomes are shown in Table 1.7.
Table 1.7: Project Economics Summary
Description |
Units |
Values |
Financial
Outcomes (Post-tax, Constant Model Terms) |
|
|
NPV
@ 10% |
US$
m |
308.73 |
IRR
|
%
|
33.99 |
Peak
Cash Funding |
US$
m |
309.18 |
AISC
|
US$/oz
|
967.90 |
Payback
(UNDISCOUNTED) - From Production Start |
years
|
1.9 |
A data table analysis has been conducted to specifically illustrate
the influence of changes in gold pricing and discount rates on the project's economic outcomes and is presented (bold) in Table 1.8 that
indicates the current base case scenario. The NPV and payback period (undiscounted, from production start) are presented on a post-tax
basis.
| // | |
Table 1.8: Data Table Analysis
|
Discount
Rate (%) |
|
Gold
Price (USD/oz) |
15% |
12.5% |
10% |
7.5% |
5% |
Payback
Period (Post-tax), years |
NPV
(Post-tax), USD M |
1,500 |
31 |
59 |
94 |
137 |
191 |
3.6 years |
1,700 |
116 |
157 |
206 |
267 |
342 |
2.5 years |
1,884 |
194 |
246 |
309 |
385 |
480 |
1.9 years |
2,000 |
243 |
302 |
373 |
460 |
567 |
1.8 years |
2,200 |
327 |
398 |
484 |
588 |
717 |
1.6 years |
2,400 |
411 |
494 |
594 |
717 |
867 |
1.5 years |
2,600 |
495 |
590 |
705 |
845 |
1016 |
1.3 years |
|
1.22.1 |
Mineral Resource Estimate |
|
· |
The data collected during the exploration, drilling and sampling programmes, including surveying, drill hole
logging, sampling, geochemical analysis, and data quality assurance, was collected in a professional manner and in accordance with appropriate
industry standards by suitably qualified and experienced personnel. |
|
· |
The geological modelling and Mineral Resource estimate were undertaken utilizing recognized deposit and industry
strategies/methodologies for the type of deposit of the Bilboes Mine. |
|
· |
The Mineral Resource is constrained in an optimized pit shell. This together with the assumptions relating
to mining, processing, infrastructure, and market factors supports the “reasonable prospects for eventual economic extraction”. |
|
· |
Based on an assessment including: - data quality and integrity, data spacing, confidence in the grade interpolation,
confidence in the geological interpretation and confidence in the estimate the relevant Qualified Person (QP) believes the Mineral Resource
estimate is robust. |
|
1.22.2 |
Mining Engineering |
|
· |
Both the modelling and the grade interpolation have been conducted in an unbiased manner and the resulting
grade and tonnage estimates should be reliable within the context of the classification applied. |
|
· |
The open pit modelling is based on suitably supported assumptions and parameters and completed utilizing appropriate
industry standards suitable for the Bilboes Project. |
|
· |
The economic modelling is supported by technical studies in mining, processing, infrastructure, environmental,
social, and marketing. Based on the inputs from these disciplines, the financial model demonstrates an economically viable mine. The economic
analysis is based on a gold price of US$ 1,884/oz. |
| // | |
|
· |
The sensitivity analyses demonstrates that the profitability of the project is most sensitive to revenue related
factors such as gold price and recovery. |
|
· |
Based on the study work completed it shows an attractive economic outcome. It is recommended that the Bilboes
Project enters into a feasibility study phase. This is estimated to cost $ 1,429,000. |
| // | |
Caledonia mandated the completion of this TRS to report the
Mineral Resources and Mineral Reserves on the Bilboes Gold Project effective as of 31 December 2023 in compliance with S-K 1300.
DRA previously issued an S-K 1300 pre-feasibility study for
the Project entitled “Bilboes Gold Project Technical Report Study”, with an issue date of May 15, 2024 and an effective date
of December 31, 2023. On June 3, 2024, Caledonia published a new technical report for Bilboes, which superseded prior technical reports
and technical report summaries for Bilboes. The new Bilboes technical report was a Preliminary Economic Assessment prepared in accordance
with Canada’s National Instrument 43-101 and did not comply with S-K 1300. The purpose of this TRS is to report mineral resources
for the Project in accordance with S-K 1300, to present the results of an IA for the implementation of open pit mining to recover the
gold mineralization and to propose additional work required for feasibility level studies.
|
2.2 |
Sources of Information |
The sources of information include historical data and reports
compiled by previous consultants and researchers of the Project and supplied by Caledonia, as well as other documents cited throughout
the report and referenced in Section 21.
|
· |
All exploration and mining permit information was supplied by Bilboes, |
|
· |
All input drilling data used for the generation of the geological and resource models were supplied by Bilboes
who also supplied all historical information including geological data, reports, and maps. The Whittle shells used to define the Mineral
Resource were created by DRA, using the latest block models supplied by DRA. |
|
· |
Information on the process was obtained from the pilot plant test work, |
|
· |
The rest of the technical information was obtained by the various consultants engaged by Bilboes |
|
2.3 |
Personal Inspections / Site Visits |
The following personal inspections / site visits were completed
on the Bilboes properties by the QP on 21 and 22 February, 2018, 20 and 22 March 2018 and 26 September 2018. After discussion with the
mine and based on the lack of any significant mine production or construction, it was deemed that site visits in 2024 would not add any
value to the work completed.
|
2.4 |
QP Responsibilities and Relationships |
The QP is not affiliated with Caledonia or any other entity
that has an ownership, royalty or other interest in the Bilboes properties.
| // | |
The Bilboes properties are located in the Matabeleland North
Province of Zimbabwe. The Isabella-McCays properties are situated approximately 80 km north of Bulawayo while Bubi is situated approximately
100 km north of Bulawayo. Bubi is 32 km due north-east of Isabella (See Table 3.1 for coordinates).
Figure 3-1: Regional Location of the
Bilboes1
The Isabella-McCays-Bubi properties comprise 130 claim blocks
covering an area of 2,731.6 ha as shown in Table 3.1.
___________________________
1 Source: Burger
et al, 2017
| // | |
Table 3.1: Bilboes Claims
Group
of Claims |
Mining
District |
Province |
No.
of Blocks |
Area
(ha) |
Coordinate
X1 |
Coordinate
Y1 |
Calcite and
Kerry (Isabella Mine) |
Bulawayo |
Matabeleland
North |
49 |
1,894.4 |
662,106 |
7,846,712 |
Ruswayi
(McCays Mine |
Bulawayo |
Matabeleland
North |
33 |
330 |
666,339 |
7,849,975 |
Chikosi
(Bubi Mine) |
Bulawayo |
Matabeleland
North |
48 |
507.2 |
684,838 |
7,865,515 |
Total |
|
|
130 |
2,731.6 |
|
|
Coordinates are in UTM Arc 1950 Zone 35K, Clarke 1880 spheroid
format.
|
3.3 |
Mineral Tenure and Title |
Bilboes claims which are wholly owned by Bilboes, consists
of 130 blocks, are of mineral interest ownership type and includes the full rights to explore, develop, and produce the minerals.
Of the 130 blocks, 49 gold and base metal blocks and a Special Mine site belong to the Isabella mining area while McCays comprise of
33 gold blocks (Figure 3.2) and Bubi consisting of 48 gold blocks (Figure 3.3). The rights were obtained through certificates of Registration
After Transfer from Prospecting Ventures, an exploration entity owned Anglo American which had pegged these claims after carrying out
exploration work. Bilboes also thereafter registered additional claims in the surrounding area. The claims are protected annually against
forfeiture through gold production and exploration work and the Company has exclusive rights to subsurface areas to produce gold from
these properties. These rights which are also transferable do not expire if the annual protection fees are paid when they become due and
these amount to US56,062 annually.
| // | |
Figure 3-2: Isabella-McCays Mine Claims
Map
| // | |
Figure 3-3: Bubi Mine Claims Map
Bilboes has been operating in Matabeleland since 1989. It holds
the necessary mining permits and complies with the terms of the Mines and Minerals Act and allied regulations with respect to all of their
claims and in particular that all of the registration certificates are valid, and the protection certificates are up to date. Bilboes
thus requires no further permits to explore or produce from the current operational areas, but further permits will be required for the
proposed haul road between Bubi and Isabella plant.
Further exploration outside the current claims will require
approvals by the EMA who may request an EIA study.
SLR Consulting based in South Africa in partnership with the
local GryinOva Environmental Consultants conducted an ESIA study for the project and an EIA certificate of approval was issued by EMA
in February 2021 and the certificate was valid for 2 years and subject to renewal on an annual basis for the duration of the operations.
The current EIA certificate expires in March 2025. The conditions
of renewal are notification to the agency of any changes in the project, compliance to the approved environmental plan and submission
of progress report on the project. There is no reason that the renewal will not be granted.
| // | |
Other project related licenses include air emissions (generators,
smelter, incinerator), explosives (purchase and storage), firearms, medicines control, public health (medical examination), water abstract
and hazardous substances (importation, transportation, storage and use), solid waste disposal which are renewed when they become due either
quarterly or annually. The conditions of renewal involve payment of applicable fees to the regulatory bodies for an amount of $70,000
per annum.
Bilboes also hold 3,935 ha of additional claims and 59,100
ha of exploration licenses referred to as Exclusive Prospecting Orders (EPOs) around Isabella-McCays-Bubi and the Gweru area. These claims
and EPOs have highly prospective targets which offer Bilboes excellent prospects for organic growth. The company has applied for an extension
of the EPOs tenure for a further 3 years after the initial 3-year tenure expired in July 2021. The decision on the EPO applications is
pending.
Political uncertainties are risks, which may lead to unfavorable
legislative and taxation framework changes, exchange control restrictions, international monetary fluctuations, civil unrest, or any other
political instability. However, the current political environment is looking favorable due to the recent reforms by the Government under
the new dispensation. It is expected that this or any other politically related risks will not affect Bilboes now or in the foreseeable
future.
All the properties belonging to Bilboes are protected in respect
of the Mines and Minerals Act. All the blocks of claims are registered with the Mining Commissioner’s office and are regularly inspected
in compliance with the mining regulations and preserved against forfeiture.
|
3.6 |
Indigenization and Economic Empowerment |
The Indigenization and Economic Empowerment Act has since been
amended and it now allows foreign entities to own 100% mining rights. Foreign shareholding will now be negotiated with investors.
All new foreign investment into Zimbabwe requires an investment
license issued by the Zimbabwe Investment Authority in terms of the Zimbabwe Investment Authority Act.
Moreover, in the mid-term budgetary review statement of 2019
the Indigenization and Economic Empowerment Act was repealed and replaced by the Economic Empowerment Act, which is consistent with the
current thrust “Zimbabwe is Open for Business".
| // | |
|
4 |
ACCESSIBILITY, CLIMATE, LOCAL RESOURCES, INFRASTRUCTURE AND PHYSIOGRAPHY |
Isabella McCays and Bubi are approximately 80 km and 100 km
directly north and northeast of Bulawayo, the second largest city of Zimbabwe with an approximate population of 655,675 (2013). All the
mines are accessed via public roads and although these are of variable quality, they are accessible by all types of vehicles. Isabella
is 110 km (1.5 hours) whilst Bubi is 140 km (2 hours) by road from Bulawayo. Bubi can also be accessed by road from Isabella
(70 km in 1 hour).
The properties lie between 1,150 m and 1,200 m above
mean sea level (amsl). The area is covered by red and grey soils characteristic of greenstone rocks in Zimbabwe. Vegetation is dominated
by scrubby Colophospermum Mopane, Acacia, and Combretum woodlands and minor occurrences of miombo with no extensive grasslands. Agricultural
activities are restricted to ranching.
Despite lying in the tropics, the climate is subtropical due
to its relatively high altitude. The mean annual temperature is 19°C. Three broad seasons are prevalent: a dry, cool winter season
from May to August; a dry, hot early summer from late August to Early November and a wet, warm summer from early November to April. Rainfall
during the wet season averages 594 mm. The climatic conditions allow for a year-round exploration and mining activities.
|
4.4 |
Local Resources and Infrastructure |
The terms of the claims tenure system in Zimbabwe confer rights
to use of the land surface for mining and construction of all related infrastructure such as housing, offices, plant, and tailings/waste
disposal facilities subject to adherence to the environmental legislation. In 2019, Bilboes obtained rights for an additional 1,128 ha
for a mine site at Isabella which will be adequate to cater for the additional sulfide mine infrastructure such as the sulfide plant,
tailing’s storage facility, waste dumps, housing, and additional office infrastructure.
There is sufficient underground water around the mines to run
the current heap-leach operations, but additional drill holes and pumping capacity will be required for the proposed sulfide-mining project.
This issue was identified in the Pre-Feasibility stage of the project, along with water-use permits.
There are 33 kV power lines within 5 km and 25 km
of the Isabella McCays and Bubi deposits respectively, that form part of the national grid, but new lines will have to be constructed
to meet the increased capacity of the proposed exploitation of the sulfides.
A 70 km kV Lynx line will be constructed from Shangani
Substation to a substation which will be constructed at Isabella.
An alternative 88 kV power line, which is sufficient for the
sulfide project, is located at Turk Mine about 40 km from Isabella McCays and 60 km from Bubi, but this line has recently had an
increased consumer load.
| // | |
Workshops, offices, and housing amenities are available for
heap leach extraction, and these will require to be upgraded for the proposed sulfide mining project.
The mines have cell phone and internet connectivity and utilize
a two-way radio system.
Generators at all mines allow continued production during load
shedding. The capacity will need to be upgraded to cater for the sulfide operation.
Zimbabwe continues to boast the highest literacy rate in sub-Saharan
Africa National examinations are written during the third term in November, with "O" level and "A" level subjects
(UK based qualification for students aged 16 and above). Currently, there are seven public universities as well as four church-related
universities in Zimbabwe that are fully internationally accredited. Zimbabwean culture places a high premium on education. Various mining
related qualification such as geology, mining engineering and mineral processing are offered at tertiary level. As a result there is a
pool of well qualified and experienced mining personnel.
Mining supplies, including mining and processing equipment,
are readily available in Zimbabwe.
| // | |
Anglo American Corporation of Zimbabwe Ltd (AMZIM), the company
that formed Bilboes Holdings (Pvt) Ltd, was later taken over by GAT investments (Pvt) Ltd in 2003 held the Isabella, McCays and Bubi claims.
AMZIM acquired the Isabella claims in 1982.
The Bilboes Properties are wholly owned by Bilboes Holdings
(Pvt) Ltd, which is 100% owned by Bilboes Gold Limited (Bilboes Gold), which was acquired by Caledonia on 6 January 2023. Prior to its
acquisition by Caledonia, Bilboes was a private company owned by three shareholders, Gat Investments (Private) Limited (Gat Investments),
Baker Steel Resources Limited (Baker Steel), and Infinite Treasure Limited (Infinite Treasure).
|
5.2 |
Historical Sulfide Mineral Resource Estimates |
In 2009, SRK undertook a Mineral Resource Estimate for the
sulfide Properties based on the drill holes and geological interpretations supplied by Bilboes.
Geological models were created for all these deposits, excluding
the oxide portions, to a depth of up to 150 m. Solid models were created from the wireframes generated and assays for gold within these
were used for geostatistical modelling and resource estimation. The Mineral Resource of 5.2 Mt containing 533,000 oz was declared to 100
mbs with mineralization from 3.5 Mt containing 240,000 oz being declared from 100 – 150 mbs.
The grade estimation for the Sulfide Projects was based on
a 2.0 g/t cut-off mineralized envelope. In general, the drill coverage was poor, with drill spacing ranging from 25 m (Bubi) to up to
100 m for McCays. In most cases there was only one hole per drill line.
Classification of the anomalies was based on the quality of
the estimate, which in turn was based on grade continuity and data spacing and was done according to the guidelines contained within the
JORC code (2012).
Estimates were validated by visually comparing the drill hole
grades to the block model grades for each section line in Datamine Studio™ (Datamine).
The results of the estimation for the classification as an
Inferred Mineral Resource (Table 5.1).
Table 5.1: Sulfide Inferred Mineral
Resources as of 2009
Deposit |
Cut-Off
(g/t) |
Tonnes
(Mt) |
Au
(g/t) |
Content
(koz) |
Bubi |
2.00 |
1.435 |
2.68 |
124 |
Calcite |
2.00 |
0.500 |
4.96 |
80 |
Castile |
2.00 |
0.902 |
4.32 |
125 |
Diana |
2.00 |
0.915 |
3.49 |
103 |
Maria |
2.00 |
0.177 |
3.10 |
18 |
McCays |
2.00 |
0.821 |
3.20 |
84 |
Total
/ Average |
4.750 |
3.49 |
534 |
| // | |
Subsequent to the 17,650 m core drilling by Anglo of 1994
- 1999, additional exploration work under Bilboes resumed in 2011 through to 2016 where an additional 20,527 m of core and 20,235 m of
RC drilling was completed bringing the total metreage to 58,412 m. The drilling culminated in an interim Mineral Resource update by Mr.
Arimon Ngilazi and Dr Anthony Martin in 2017.
These results are presented in Table 5.2 and Table 5.3, respectively.
| // | |
Table 5.2: Sulfide Mineral Resources
(31 March 2017) 0.0 g/t Au Cut-Off Grade
Property |
Indicated |
Inferred |
Mass
(Mt) |
Au
Grade (g/t) |
Au
(kg) |
Au
(Moz) |
Mass
(Mt) |
Au
Grade (g/t) |
Au
(kg) |
Au (Moz) |
BUBI |
29.96 |
2.20 |
65,912 |
2.12 |
9.05 |
1.90 |
17,195 |
0.55 |
ISBN |
12.07 |
2.19 |
26,433 |
0.85 |
1.55 |
2.01 |
3,116 |
0.10 |
ISBS |
7.90 |
2.43 |
19,197 |
0.62 |
0.51 |
2.62 |
1,336 |
0.04 |
MCCAYS |
3.48 |
2.44 |
8,491 |
0.27 |
7.07 |
1.97 |
13,928 |
0.45 |
Total |
53.41 |
2.25 |
120,034 |
3.86 |
18.17 |
1.96 |
35,575 |
1.14 |
Table 5.3: Sulfide Mineral Resources
(31 March 2017) 0.9 g/t Au Cut-Off Grade
Property |
Indicated |
Inferred |
Mass
(Mt) |
Au
Grade (g/t) |
Au
(kg) |
Au
(Moz) |
Mass
(Mt) |
Au
Grade (g/t) |
Au
(kg) |
Au (Moz) |
BUBI |
28.05 |
2.27 |
63,674 |
2.05 |
8.66 |
1.93 |
16,714 |
0.54 |
ISBN |
9.94 |
2.53 |
25,148 |
0.81 |
1.29 |
2.27 |
2,928 |
0.09 |
ISBS |
7.05 |
2.60 |
18,330 |
0.59 |
0.44 |
2.86 |
1,258 |
0.04 |
MCCAYS |
2.55 |
3.19 |
8,135 |
0.26 |
5.58 |
2.38 |
13,280 |
0.43 |
Total |
47.60 |
2.42 |
115,286 |
3.71 |
15.97 |
2.14 |
34,181 |
1.10 |
| // | |
|
5.3.1 |
Oxide Mineralization |
There are early records of insignificant gold production for
the Isabella Mine prior to 1982. In its first year of operation the Isabella open pit operation produced 170 kg of gold from a monthly
rate of 15,000 t of ore. At start of production there were three pits with a Mineral Reserve life of 18 months and as of 31 December 2023,
the Mine had treated 6.6 Mt of oxides at 1.15 g/t (243 koz) and recovered 150 koz of gold inclusive of re-leached gold from the old
heap leach pads. The bulk of the production from Isabella was from uncrushed ore with only 37 koz of gold being recovered from 2.5 Mt
of crushed oxide ore after the installation of a crushing plant in 2007.
Bubi was commissioned in 1997 at 25,000 t per month of oxide
ore and produced 9.5 koz of gold in its first year. Mining activities were suspended at Bubi Mine in 2007 after running out of oxide ore.
Gold production from that period to 2013 has been from re-leaching of the old heaps. Progressively inclusive of re-leached gold from the
old heap leach pads, the mine has produced 85 koz of gold as at end of December 2023 from 4.3 Mt of oxide ore at 1.00 g/t (138 koz). All
the ore at Bubi Mine was treated without crushing. There has not been any mining at Bubi from 2005 after the exhaustion of oxides until
the commencement of re-leaching activities at the beginning of 2019.
As a result of regional exploration by Prospecting Ventures
(PV), an Anglo American Corporation exploration company based in Zimbabwe at the time, a new gold deposit was discovered at McCays in
1997. In 1998 production from an open pit, heap-leach mine started. Further exploration work within the claims area during the operational
phase of the mine was added to the Reserves until depletion and temporary closure in 2002. No mining activities took place between 2002
and 2012 at McCays. Gold production was through re-leaching from the year 2004 until 2009. No gold production occurred from 2010 to 2012.
Activities commenced after the recapitalization of Bilboes in 2013. Cumulative gold production from inception at McCays was 57 koz) as
of 31 December 2023. This included the re-leached gold from the old heap leach pads from treating 2.2 Mt of oxide ore at 1.15 g/t (80
koz). Inclusive of this, an estimated 24 koz) of gold was recovered from 1,032,374 t of crushed oxide ore after the installation of a
crushing plant in 2013. The oxides at McCays are finished and only re-leaching activity is taking place.
Prior to the open-pit exploitation of the Isabella Mineral
Resource by Bilboes, the Calcite Mine (underground and now part of the Isabella strike) produced 559 kg of gold at an average recovered
grade of 8.2 g/t.
| // | |
The production from Bilboes mines including from inception
to 31 December 2023 is presented in Table 5.4. Bilboes has produced some 95,877 oz of gold from the four mines since the takeover of
the company in 2003 to 31 December 2023.
Table 5.4: Production Data from Bilboes
Mines to 31 December 2023
|
Start-up
Date |
Ore
Treated (kt) |
Grade
(g/t) |
Au
Recovered (koz) |
Isabella |
1989 |
6,575 |
1.15 |
150.3 |
Bubi |
1997 |
4,342 |
1.00 |
84.6 |
McCays |
1998 |
2,176 |
1.15 |
57.0 |
When |
2005 |
184 |
0.78 |
1.9 |
Total |
13,278 |
1.09 |
293.7 |
| // | |
|
6 |
GEOLOGICAL SETTING, MINERALIZATION AND DEPOSIT |
Geology in Zimbabwe can be divided into three main areas, the
Archean, the Proterozoic, and the Phanerozoic (Figure 6-1).
Source: Mugumbate, unknown year
Figure 6-1: Greenstone Belts and known
Gold Deposits in Zimbabwe
Rocks from the Archean era in Zimbabwe occupy most of the Zimbabwe
Craton, an ancient stable continental block. This is the basement and primarily comprises granites and gneisses with remnants of volcano-sedimentary
piles known as Greenstone Belts. Greenstone Belts cover approximately 60% of the land surface of Zimbabwe. The Greenstone Belts are renowned
for their rich variety of Mineral Resources as shown in Figure 6-1
In Zimbabwe, the Proterozoic era followed immediately after
the emplacement of the Great Dyke intrusion at the end of the Archean era. The Great Dyke is a layered mafic to ultramafic intrusion akin
to the Bushveld Complex in South Africa. It was emplaced at the end of the Archaean era at approximately 2,500 mega annum (ma). It has
a strike length of 550 km and ranges in width from 4 km to 11 km. It cuts across the entire Zimbabwe Craton in a roughly N-S
direction as shown in Source: Mukaka et al 1998.
Figure 6-2. The Great Dyke hosts world-class reserves of Platinum
Group Metals (PGMs) and chrome ore.
| // | |
Source: Mukaka et al 1998
Figure 6- 2: NNE Trending Great Dyke
Cutting Across the Zimbabwe Craton
| // | |
There are three metamorphic mobile belts that border the Craton
to the north-east, south, and north-west. The neo-Archaean Limpopo mobile belt borders the Craton on the southern boundary. The paleo-Proterozoic
Magondi mobile belt borders the Craton to the north-west while the neo-Proterozoic Zambezi mobile belt borders the Craton to the north
(Figure 6.2). These metamorphic belts are hosts to economic metamorphic minerals. They also host several gemstones, precious, and base
metals. To the east are the Umkondo group sediments which were deposited in a large basin and are capped by younger dolerite sills and
basaltic flows. The Umkondo sediments host the Chiadzwa placer diamond deposits.
Source: Gore et al 2009
Figure 6- 3: Geological Map showing
the Zimbabwe Craton and Mobile Belts
The Phanerozoic consists of several sequences of sedimentary
rocks covering the peripheries of the Craton. Included in the Phanerozoic are sedimentary basins: the Permian - Triassic Jurassic Karoo
Supergroup, Cretaceous sediments, and Tertiary to recent sand of the Kalahari.
| // | |
Source: Mugumbate, unknown year
Figure 6-4: Sedimentary Basins of Zimbabwe
|
6.2 |
Regional Geology as it Relates to the Bilboes Properties |
The Bubi Greenstone Belt covering the Bilboes Properties consists
of volcanic rocks of the Upper Bulawayan Group capped by sedimentary sequences of the Shamvaian Group locally represented by Mdutjana
and Dagmar Formations respectively (Source: Ngilazi and Martin 2017
Figure 6.4). The deposits occur within the meta-volcanic and
meta-sediments close to the contact between these two stratigraphic units.
| // | |
Source: Ngilazi and Martin 2017
Figure 6-5: Regional Geological Map
showing Bilboes Properties
| // | |
The Bilboes stratigraphic presentation is depicted in Figure
6.5.
Figure 6-6: Bilboes Site Stratigraphy
Mineralization at Bilboes’ four properties are Archaean
lode, structurally controlled deposits. It consists of silicified stock-works/veins. The veins comprise pyrite and arsenopyrite. Gold
is disseminated within the sulfide mineralization and is refractory. Pyrite is the dominant sulphide mineral, with minor arsenopyrite
at Isabella and McCays, with the exception of the Isabella North orebodies where an equal proportion of pyrite to arsenopyrite is evident.
At Bubi the dominant sulphides is pyrite with minor arsenopyrite. The mineralized zones are often subparallel to each other and are hosted
in a much broader shear zone. The best mineralized zones are associated with brecciation and silicification.
The sulphide tends to weather readily and all of the deposits
are covered by oxide caps to a depth of 12 m to 50 m which are readily amenable to heap-leach extraction.
Orebody widths at Isabella and McCays range from 5 m to 20
m and are wider near surface. Individual orebodies have strike ranges from 75 m to 500 m and are typically in en echelon pattern in a
northwest to south-eastern pattern (Figure 6.6). The oxide cap is deepest at Isabella where the range is 12 m to 50 m. The overall mineralized
strike is 4,400 m.
The oxide-sulphides interface at Bubi is shallow in the southwest
at about 10 m to 12 m below surface and increases to 30 m in the central parts and to 40 m in the northeast (Figure 6.7). Orebody widths
vary from 10 m in the southwest to as wide as 100 m in the central portions of the claims. The overall mineralized strike is 2,950 m.
| // | |
Figure 6-7: Geological Cross Section
through the Isabella and McCays Deposit
Figure 6-8: Geological Cross section
through the Bubi Mine
| // | |
Mapping has been conducted progressively at the Bilboes mines
since commencement of oxide gold operations, with the latest exercise being conducted between January and September 2018. Below are some
of the maps produced for Bubi (Figure 7.1) and the Isabella McCays area (Figure 7.2). Mapping was done to decipher surface and in-pit
geological and geotechnical information, critical for structural and alteration interpretation of mineralized units and in aiding pit
geotechnical slope stability studies.
Figure 7-1: Map of the Surface Geology
at Bubi
| // | |
Figure 7-2: Map of the Surface Geology
at Isabella McCays
Trenching was conducted across all deposits as part of exploration
work for the purposes of defining near surface geology and mineralization envelopes within the oxide horizons. The trenches were sampled
generally on a 1 m to 2 m interval and analysed by the bottle roll method (excluded fire assay of the residual tails). These assays were
used to help in the projection of oxide ore envelopes and excluded from any Mineral Resource estimation. Channel sampling was also done
in all accessible sections of the pits during 2017, which also assisted in the projection of mineralized envelopes in the oxide and transition
ore horizons, but the assays were also not used for Mineral Resource estimation.
|
7.3 |
Ground Geophysical Surveying |
Ground Magnetics and Induced Polarization Geophysical surveys
were conducted at the Isabella North deposit by PV as part of the oxide ore exploration in 1996. The anomalies were followed up with oxide
trenching and drilling. The oxide drilling data forms part of the depth interpretation of the Bilboes deposits from oxide through transitional
and sulfide horizons. Further geophysical surveys were conducted in the Kerry West claims located west of the Isabella South claims and
Kerry North claims, between Isabella North and McCays. Further drilling is outstanding on these targets and these offer potential for
oxide and sulfide resources.
|
7.4 |
Prospecting and Sampling |
Early exploration works targeted oxide mineralization and includes
soil sampling, trenching, and drilling. Assays from this work were not used in the sulfide Mineral Resource estimate but were used to
guide the interpretation of the ore outlines at depth.
| // | |
|
7.5.1 |
Sulfide Exploration |
Drilling of the sulfides to provide data for the Mineral Resource
estimate was completed in three phases:
|
· |
Phase 1: Anglo American Corporation between 1994 and 1999, |
|
· |
Phase 2: Bilboes between 2011 and 2013, |
|
· |
Phase 3: Bilboes between December 2017 and November 2018. |
Phase 1: Anglo explored the sulfide potential
beneath the oxides between 1994 and 1999. The results of widely spaced core drilling of the sulfides were used by Anglo American to estimate
a non-compliant Mineral Resource for this mineralization and delineated 4.7 Mt at a grade of 3.49 g/t and containing 533,000 oz of gold
over a 3,400 m strike to a vertical depth of 120 m from 17,650 m of core drilling.
Phase 2: Between 2011 and 2012, Bilboes completed
further exploration on the sulfides with 16,230 m from 69 core holes and 14,021 m from 101 Reverse Circulation (RC) holes in 2013
and extended the strike to 7,000 m and achieved a vertical depth of 160 m for the mineralization.
Phase 3: An additional 34,987 m of drilling,
split as 17,015 m from 129 core holes and 17,972 m from 178 RC holes was completed between December 2017 and November 2018. This was largely
an infill drilling programme for a Mineral Resource upgrade across all deposits at Isabella, McCays and Bubi and achieved a vertical depth
of 200 m. The total project drilling conducted over the three phases is 93,400 m of core and RC holes with an additional 2,500 m of core
drilled for geotechnical work for the PFS.
Sulfide mineralization underlies all the oxide deposits at
variable depths from 15 mbs to 50 mbs. Two exploration campaigns account for historical exploration of sulfide gold deposits at Bilboes.
Both exploration campaigns were headed by PV. The first drilling campaign occurred in 1994/5. During this campaign 24 drill holes were
completed. In the second drilling campaign which took place in 1997/9, 99 drill holes were completed. A total of 123 holes totalling 17,650 m
(12,650 m core and 5,000 m percussion) were drilled at Isabella, McCays and Bubi covering a strike of 3,440 m.
Drill holes depths varied between 70 m and 350 m
for the core holes, with the holes being collared through percussion drilling to a depth of 50 m. The percussion holes were largely
used to estimate the oxide Mineral Resource and to define the oxide / sulfide interface. Only core drill holes were included in the sulfide
databases. The drill line spacing varied between 25 m and 100 m with 25 m between holes along these lines.
The initial holes drilled by PV before 1995 targeted the Calcite
(5), Castile (9) and McCays (10) deposits. The majority of these were drilled at 45° inclinations and from hanging wall positions
of the mineralized zone. A few exceptions resulted from unavailability of a suitable collar position due to the open pits. Sampling was
limited to the visually recognizable alteration zones resulting in approximately 30% of the total hole length being sampled.
At the Diana pit (Isabella Mine), 14 holes were drilled, two
spaced at 10 m and two at 50 m with the rest spaced at approximately 25 m intervals. One hole was drilled on each line;
all from the hanging wall with one from the footwall. The mineralized intersections occurred at 45 m to 95 m with one intersection
at 125 m (DE15-530S). The footwall of the mineralization intersected was at 169 m to 182 m.
| // | |
At Maria pit (Isabella) all six holes (1998-9) were drilled
from the hanging wall with five holes spaced at 25 m and the rest at 50 m. The average intersection depths occurred at 45 m
from surface and geological envelopes were modelled down to 100 m from surface. Two parallel, mineralized zones steeply dip at 70°
to SE and the hanging wall ore body stretches along the entire length of the pit, but the footwall zone is restricted to the eastern end
of the strike.
A total of 15 holes were drilled along the Calcite strike from
the footwall and two from the hanging wall at 50 m to 120 m line spacing. The deepest intersection occurred at 130 m from
surface and the intersection depths ranged from 50 m to 120 m. The eastern end of the strike remains open.
The Castile drilling intersected two mineralized zones that
were modelled to 110 m from surface, but the mineralization remains open on all sides. Two holes intersected a significant parallel mineralization
(6.68 g/t over 10.59 m and 4.90 g/t over 9 m) in the footwall of the two main zones. Both holes ended in mineralization and require further
investigation in future. These holes have not been investigated in the 2017/8 drilling campaign because they lie outside of the proposed
open pit.
The 25 holes at Bubi covered a strike of 900 m on lines 25
m apart except for two holes which were spaced at 50 m and 100 m. All the holes (but one) were drilled from the hanging wall in the same
SE direction inclined at 45°. Three distinct, parallel zones were identified but these were discontinuous along strike and the mineralization
remained open ended towards the southern strike of 1,500 m. The oxide cap is at 15 m to 30 m from surface and only 10 m
in the southern strike. Drilled intercepts start at 20 m to 80 m and the deepest occurs at 130 m. The geological models
were done to a vertical depth of 170 m from surface.
At McCays 23 holes were drilled in the pit and two mineralized
zones were defined along strike but broken up mid-way. Drill spacing was at 50 m to 100 m with a few lines having two holes
each. All holes were drilled from the hanging wall but at varying inclinations from 45° to 60°. The geological models were created
to 160 m vertical depth with average intersections occurring at 75 m. Two of the holes at McCays had deep (but low grade) intersections
that do not form part of the established pattern of mineralization.
A summary of the drilling completed is presented as Table 7.1
with the drill hole distribution being presented in Figure 7.3.
| // | |
Table 7.1: History of Sulfide Project
Core Drilling 1994 - 1999
Mine |
Deposit |
Pit |
No.
of Holes |
Total
Strike (m) |
Drilled
Length (m) |
Depth
Achieved (m) |
Isabella |
Isabella
North |
Diana |
14 |
315 |
2,200 |
150 |
Calcite |
17 |
575 |
2,600 |
150 |
Isabella
South |
Castile |
37 |
450 |
5,100 |
100 |
Maria |
7 |
200 |
550 |
70 |
McCays |
McCays |
Central /
Eastern |
23 |
1,000 |
4,000 |
100 |
Bubi |
Bubi |
North |
25 |
900 |
3,200 |
120 |
Total |
123 |
3,440 |
17,650 |
|
Source: Ngilazi and Martin, 2017
| // | |
Isabella North (ISBN) |
Isabella South (ISBS) |
|
|
|
|
Bubi |
McCays |
green = Percussion drilling
blue = Diamond Drilling
red = Reverse Circulation drilling
|
|
Figure 7-3: Plans Showing the Drilling
for the Various Areas
| // | |
7.5.2
Logging and Sampling Procedure
There are no written accounts of the historic sampling procedures,
but Mr. Chimedza, who has been employed by Bilboes since 1996, was closely involved with the exploration of the sulfide deposits. He confirms
that the sampling of the core followed Anglo American Corporation standard procedures. This was considered to have been sufficiently accurate
for the purpose of reporting of Inferred Mineral Resource estimates contained in the 2009 Mineral Resource declaration.
The geological logging included descriptions of lithologies,
structures, alteration, and visible sulfide mineralization. The information was entered into core logging sheets and mineralized zones
were identified. All geological boundaries were defined with reference to the drill length. On completion of assaying, the gold results
for each sample were recorded on the log sheets for easy reference. Core recoveries were recorded, and any depth discrepancies were checked
and corrected. Geotechnical logging, including the RQD index and fracture spacing, was also undertaken.
Bilboes has hardcopy and digital datasets of all information
except for the geotechnical logs for which only hard copies are available.
Core was fitted together, and a longitudinal line drawn to
guide splitting. Within the mineralized zones sample intervals were marked between 0.5 m and 1.0 m, taking cognizance of geological and
structural boundaries, and sampling was continued at 1 m intervals to 5 m on either side of the mineralization.
All the visually recognizable mineralized portions of the drill
holes were cut, half core sampled, and assayed with well over 10,000 samples being assayed for gold.
|
7.6 |
Hydrology and Hydrological Drilling |
The project site falls within the Bembezi river sub-catchment
which drains north towards the Zambezi River. The Gwayi catchment largely comprises the Northern Matabeleland area of hydrological zone
A.
Daily and monthly rainfall were obtained from the Nkayi station
from the Meteorological Services Department of Zimbabwe (MSD-Z) for 38 hydrological years (from 1980 to June 2018) and were analysed to
determine the long-term monthly averages, minimum and maximum monthly rainfall. The Mean Annual Precipitation (MAP) is 657.0 mm, the wettest
hydrological year saw 53% more rainfall than the MAP and the driest hydrological year saw only 60% of the MAP. The driest period was associated
with the drought experienced in the 1990s.
Data from the Nkayi station was adopted as the design data
owing to the weather station having an acceptable length of record of monthly rainfall data and being located closest to the site and
at a similar altitude.
Ten years of monthly pan evaporation measurements for Bulawayo
Goertz were provided by the MSD-Z. A pan coefficient of 0.75 was adopted for the conversion of Epan measurements to a reference evapotranspiration.
The annual maximum rainfall analysis for various duration storm
events (from 24 hours up to 7 days) was undertaken on the 38 years of daily rainfall records supplied by the MSD-Z.
| // | |
The Generalized Extreme Value (GEV) distribution was then fitted
to the annual maximum series to estimate storm depths for events with an annual probability of occurrence of up to 1:10,000 (0.01%).
No hydrological drilling has been undertaken. For pits that
contained water ingress, a bathymetric survey was done to determine pit bottom.
|
7.7 |
Geotechnical Drilling |
A total of 18 geotechnical drill holes: ten at the Isabella
McCays and five at Bubi, varying in depth from a minimum of 120 m to a maximum of 260 m were logged. The cumulative length of the drill
holes at Isabella McCays Isabella McCays was about 1.67 km; and those at the Bubi was about 0.88 km.
SLR Consulting (Africa) (Pvt) Ltd, from South Africa was contracted
by DRA to conduct a detailed geotechnical study across all the sulfide deposits. SLR Rock Engineers visited site at various stages of
the geological drilling campaign during 2018 with the following tasks being conducted; review of geological and geotechnical data; geotechnical
logging of core and the collection of intact rock samples for testing. Structural data was collected by both the Acoustic and Optical
Televiewer from the geotechnical boreholes. Packer testing was also conducted in each borehole to determine the hydrogeological parameters
of the rock mass, for groundwater modelling. Based on the analysis of the geological aspects of the deposits which included rock mass
characterization, hydrogeology, and structural geology, a geotechnical model was developed for pit design parameters. Using these design
parameters, kinematic, empirical and limit equilibrium analysis was conducted to determine the optimal slope configuration for the various
deposits.
| // | |
|
8 |
SAMPLE PREPARATION, ANALYSES AND SECURITY |
The recovery of samples from the RC and core drill rigs was
done in accordance with laid down procedures adequate for the purposes of reporting of Mineral Resources. Once field measurements, markings
and numbering and recording of critical information were completed, the core samples were transported daily from the drill site to the
core yard and RC samples to secure metal containers to ensure security and avoid tampering, damage, loss, or contamination. The core was
adequately secured to prevent damage, loss, or mix-up during transportation. Wet RC samples were collected in calico bags to allow water
to drain out and minimize sample loss prior to sun drying in metal trays in a securely fenced section of the core shed which was free
from dust ingress and other forms of contamination. Core samples were half split using a core saw and the samples averaged 2 - 3 kg. The
core sizes were largely NQ with a few HQ cores being encountered at the start of drill holes. RC samples were collected by way of a Jones
riffle splitter and the aliquots also averaged 2 - 3 kg. After sampling, excess cores and RC samples have been stored at the mine in secure
sample containers and the core shed and have been retained for future use. All samples were labelled appropriately prior to dispatch.
No further sample preparation was done at site and the half cores and riffle split RC samples were transported to the external accredited
Laboratory. Transportation of samples to the Assay Laboratories was done utilizing Bilboes vehicles accompanied by a senior member of
the technical team followed the laid down chain of custody procedure between the company and the Lab to ensure sample security in transit
and proper handover-takeover. Transportation of samples to the Lab was done on the same day within working hours with no unnecessary stopovers
along the way to reduce risk of loss, contamination, or damage.
DRA reviewed the procedures for sampling, sample preparation
protocol, sample handling and storage and are of the view that these are adequate for the purposes of reporting of Mineral Resources contained
herein. Bilboes and an Independent SRK Consultant also visited and inspected the laboratories used in the analyses and can confirm that
these also followed the correct procedures for sample preparation.
Independent SANAS accredited laboratories were used in the
analyses of samples. Samples were analysed for gold by Fire Assay on 50 g pulp aliquots and completed by Atomic Adsorption spectrophotometry
method. Samples with grades at 3 g/t and above were repeated by the gravimetric finish.
Performance Laboratory (PLZ) in Harare, was selected as the
primary laboratory (accreditation number T0533) ZIMLABS Laboratory located in Harare (accreditation number T0339), and Antech Laboratories
(Antech) located in Kwekwe (accreditation number T0411) were used for check analyses. All Laboratories are in Zimbabwe and have all since
migrated to the Southern African Development Community Accreditation Service “SADCAS” which accreditation is in accordance
with ISO/IEC 17025 system. Current accreditation are:-
|
· |
Performance Laboratory - TEST-500070 issued on 3 June 2022, |
|
· |
ZIMLABS - TEST-50010 issued on 20 February 2015, |
|
· |
Antech - TEST-50030 issued on 1 June 2023. |
| // | |
At all times during sample collection, storage, and shipment
to the laboratory facilities, the samples were in the control of Bilboes. The samples were then trucked to Performance Laboratories in
Harare for geochemical analysis.
During the 2018 drilling and sampling campaign, all analytical
results were emailed by Performance Laboratories to Bilboes. Comparisons were done between the drilling database received from Bilboes
and the assay results received from Performance Laboratories to verify the database.
All the laboratories that conducted the sampling and analytical
work were independent of Bilboes. Performance Laboratories in Zimbabwe is an entity of SGS. SGS produces impartial results that are considered
suitable for Mineral Resource estimation.
As part of their QA/QC protocols to test for the precision
of the analytical process, Bilboes inserted CRMs, blanks into their sampling stream, and created duplicates for re-analysis. During the
2017 Mineral Resource review of the Bilboes properties, DRA did a thorough review of the QA/QC protocols. The findings of that review
concluded were that the protocols employed at Bilboes were adequate and the database was deemed fit for the purposes of geological modelling
and Mineral Resource estimations. The review was in respect of all protocols from commencement of drilling campaigns by Bilboes in 2011
till completion in 2018.
CRMs were sourced from AMIS in South Africa, Geostats in Australia,
and Rocklabs in New Zealand. Silica powder from AMIS and local dolerite were used as blanks. Bilboes utilized two types of duplicate materials:
a Pulp Duplicate (LPR) and a Coarse Duplicate (LCR). In a batch of twenty samples, at least four out of the twenty samples were control
samples. This represents an insertion ratio of at least 20%. If more than 20% of CRM results in a batch returned results that fell outside
the allowable deviation of the recommended value; all results from that batch were failed and re-analysed.
For the 2018 sampling campaign, Silica powder and local dolerite
were used as blank material. AMIS0415, AMIS0439, and AMIS0484 were used as silica blanks. During the 2017 review by DRA, 272 blanks were
present in the database. An additional 859 blanks were added to the database for the 2018 campaign, taking the total number of blanks
to 1,131.
A detection limit of 0.02 g/t was set for the exercise while
the upper acceptable limit was set at 0.1 g/t for the silica blanks and 0.15 g/t for the field blank. All samples for AMIS0415
and
AMIS0439 plotted the allowable upper limit of 0.1 g/t. Only one sample returned a gold value more than the 0.1 g/t allowable upper limit
for AMIS0484. Similarly, with the field blank, only one sample returned a gold value more than the allowable 0.15 g/t upper limit.
CRMs were sourced from African Mineral Standards (AMIS) in
South Africa and Geostats Pty Ltd in Australia for the previous drilling campaign.
For the 2018 drilling campaign, CRMs were sourced from AMIS
- AMIS0440, AMIS0441, AMIS0473, AMIS0525, and AMIS0526. These represent the grade distribution observed at Bilboes. AMIS0473 has a recommended
grade of 0.41 g/t, for AMIS0526 the recommended grade is 1.03 g/t, 1.74 g/t for AMIS0440, 2.44 g/t for AMIS0441, and 8.04 g/t for AMIS0525.
| // | |
Most of the control samples of AMIS0440 plot within three standard
deviations of the recommended mean value of 1.74 g/t. some seventeen samples plot outside the allowable three standard deviations limit.
This is to be expected of a low/middle grade CRM.
All the control samples representing CRM AMIS0441 plot within
three standard deviations of the recommended mean value of 2.44 g/t with most samples lying within two standard deviations.
For AMIS0473 all the control samples lie within one standard
deviation of the mean of 0.41 g/t. For AMIS0525 all the control samples, bar one, plot within two standard deviations of the mean value
of 8.04 g/t. However, a slight positive bias is observed for AMIS0525 with a majority of the samples lying above the recommended mean
value. Five samples lie outside three standard deviations of the recommended mean value of 103 g/t for CRM AMIS0526
Two types of duplicates were employed in the 2011 to 2018 drilling
and sampling campaigns i.e., Lab repeats and field duplicates. The former is made up of LPR and LCR. There were 721 LPRs and 875 LCRs
in the database for the 2018 campaign. The majority of samples were within a 15% margin. Samples that fell outside of the 15% margin could
be attributed to the inherent nugget effect of the deposit.
Performance Laboratories was used as the primary laboratory
for analysis in the recent drilling campaigns from 2011 to 2018. To check the reliability of the results obtained from Performance Laboratories,
ZIMLABS and Antech Lab were used as umpire laboratories. The results show the acceptable correlation between the primary laboratory and
the umpire laboratories.
The QP is of the opinion that sample preparation, security
and analytical procedures were adequate.
| // | |
DRA engagement with Bilboes began with a review of the previous
Mineral Resource estimate. During the review process, rigorous tests were conducted to verify the integrity of the Bilboes database. A
recommendation from the review process by DRA was to implement a commercial data management software, to which Bilboes complied by acquiring
Datamine™ Fusion database software for the capture, storage, and management of drill hole information. This Fusion database was
implemented prior to the start of the 2018 drilling campaign.
|
9.2 |
2017/2018 Drilling Campaign |
Before commencement of the 2017/2018 drilling campaign in addition
to the Datamine™ software already in place Bilboes utilized Fusion database software for the capture: storage and management of
drill hole information.
The 2018 drilling programme contained 41 RC and 55 DD holes
for ISBN, 27 RC and 20 DD holes for ISBS, 76 RC and 55 DD holes for McCays, and 40 RC and 13 DD holes for Bubi. With regards to the 2018
data, DRA visited the site during drilling and performed various checks to verify the integrity of the collar co-ordinates, logging and
sampling procedures, and assay results. Collar locations in the field were clearly marked. The mineralisation zones were observed in the
cores as well as from outcrops in the surface mining pits.
The core logging and sampling processes at the core storage
facility were observed to be consistent with industry standards. Each hardcopy log is audited and signed-off by a senior geologist prior
to being used in modelling and estimation.
The data collected during the exploration, drilling and sampling
programmes, including surveying, drill hole logging, sampling, geochemical analysis, and data quality assurance, was collected in a professional
manner and in accordance with appropriate industry standards by suitably qualified and experienced personnel.
The data was reviewed and validated by the QP who concluded
that the data is suitable for the construction of the geological model and for the purposes used in this TRS.
| // | |
|
10 |
MINERAL PROCESSING AND METALLURGICAL TESTING |
|
10.1 |
Test Work Programme Overview |
The metallurgical test work was concluded in different phases
over a period extending from September 2013 to March 2019 and involved various independent laboratories and consultants as outlined in
Table 10.1.
Table 10.1: Test work Program Outline
Phase |
Test
work Description |
Done
By |
Supervision
and Oversight |
Date |
1A |
Sample characterization detailing mineralogical
and chemical analysis |
Mintek, South Africa |
Bilboes, MMC and MDM Engineering |
September 13 to December 13 |
1B |
Comminution test work done on the two composites
namely Composite 1 (Bubi ore) and Composite 2 (combination of Diana, Calcite, Castile, Maria and McCays ores) |
Mintek, South Africa |
Bilboes, MMC and MDM Engineering |
January 14 to April 14 |
2 |
Selection of a process route covering gravity
amenability tests, flotation optimization and treatment of the sulfide flotation concentrates via POX, Bio-Oxidation and Ultra-fine grinding
followed by cyanidation |
Mintek and Suntech, South Africa |
Bilboes and MMC |
May 14 to September 14 |
3 |
Variability flotation
tests and bulk flotation concentrate production for additional BIOX® and gold leach tests |
Suntech and SGS, South Africa |
Bilboes, Minxcon and MMC |
October 15 to August 16 |
4A |
Laboratory and Pilot plant test work campaigns
on the different ore types to generate additional flotation kinetics and grind data, bulk concentrates for BIOX® pilot plants, flotation
design parameters and validate flowsheet |
MMC at the client's project site in Zimbabwe |
Bilboes and DRA |
April 18 to September 18 |
4B |
Review, modelling and simulation of laboratory
and pilot plant test results |
EMC, South Africa |
Bilboes, MMC and DRA |
October 18 to March 19 |
Phases 1 to 3 constituted preliminary test work and Phase 4
(Pilot plant), supplementary laboratory test work, modelling, and simulation the definitive test work.
|
10.2 |
Discussion of the Results |
The mineralogical and chemical analyses of the ores conducted
on the individual and composite samples is summarized as follows:
|
· |
Gold content in the samples varied from 1.8 mg/kg to 6.8 mg/kg. |
| // | |
|
· |
All samples contained high concentrations of Si, Al, Ca, Fe and As. Total sulfur concentrations in the samples
varied from 1.2% to 5.3% and significant amounts of it were sulfide species. |
|
· |
The Total carbon in the ores was detected at 1.3% - 5.3% and was mainly present as carbonate. Organic carbon
was low for all samples tested, indicating low potential for preg-robbing. Carbon (as carbonate) content was high, especially for Bubi
and McCays pits (double amount in comparison to other composite samples). Carbonate concentrations of between 7.4% and 18.4% were detected
in the samples. |
|
· |
The Total sulfur content in the samples was found to be mainly in the sulfide form with the lowest content
of 0.69% in the McCays ore and the highest content of 2.65% in the Bubi ore. The concentration of elemental sulfur and sulphate was very
low. High As content was detected in all samples which highlighted the importance of investigating as behavior during the processing steps
and to consider possible environmental issues in deciding on process route and economics. The As content in the McCays ore was disproportionately
higher than the other pits. |
|
10.2.2 |
Mineralogical Characterization |
|
· |
Diagnostic leach results showed that gold recovery via direct cyanidation was low, varying from 25% to 50%
and Au locked in sulfides and carbonate minerals varied from 46% to 72%. |
|
· |
Bulk Modal Analysis (BMA) showed that quartz, feldspar, and mica were present in major to intermediate amounts
in all the samples, followed by major to minor amounts of carbonates. Sulfide minerals, pyrite and arsenopyrite, were present in minor
to trace amounts throughout all samples. All other mineral phases are present in trace amounts in all samples. |
|
· |
The Au bearing minerals identified in this study were electrum (AuAg) and native gold (Au). Native gold and
electrum are variably distributed throughout all samples. |
|
· |
Most Au-bearing grains reported to the 0 μm -10 μm size class fraction and a smaller quantity in the
10 μm -15 μm size class fraction. |
|
· |
Pyrite was the dominant BMS mineral present as majority of the samples followed by arsenopyrite (from 5 to
58%) and trace amounts of other sulfides (sphalerite, pentlandite, chalcopyrite, chalcostibnite, ullmannite, gersdorfiite and galena) |
|
· |
The majority of all BMS mineral grains (>50 mass%) in all samples reported to the finer, 0 μm -21 μm
size classes, with lesser amounts reporting to the coarser size classes. |
|
· |
The majority (>80 mass%) of pyrite, arsenopyrite and other sulfides had free surface with lesser amounts
being associated with other mineral phases in all the samples examined. |
| // | |
Comminution test work showed that Isabella and McCays samples
with Bond Ball Work Index (BBWi) values ranging from 15.70 kWh/t to 17.81 kWh/t and A*b values ranging 27.50 to 32.80 could be classified
as being hard, while Bubi ore with a BBWi value of 21.45 kWh/t and A*b value of 19.0 was very hard. All samples were characterized as
being moderately abrasive with Ai indices ranging from 0.22 to 0.42.
|
10.3 |
Process Route Identification |
Gravity amenability tests indicated poor gold recoveries and
varied from 14% to 22% at 0.5% mass pull. Gravity separation at higher mass pull provided higher gold recovery but still was not a feasible
option.
|
10.3.2 |
Preliminary Flotation |
Initial milling and flotation results indicated high gold recoveries
of 89% - 97% with high mass pulls ranging from 10%- 15%, low concentrate grades of 12 g/t - 20 g/t Au and unacceptable high levels of
carbonates in the range of 7% - 13% which were bound to negatively affect the down-stream gold recovery process. The test work established
that the ores can be easily floated with good recoveries at grinds ranging from 80% of 106 µm - 75 µm and that flotation optimization
with respect to mass pulls, concentrate grade and other concentrate quality metrics was required.
|
10.3.3 |
Flotation Optimization |
Subsequent flotation optimization tests involving the addition
of depressant and 1 and 2 cleaning stages improved the overall flotation performance with recoveries ranging from 88% to 94%, with mass
pulls ranging from 4% - 12%, concentrate grades of 50 g/t – 120 g/t Au and acceptable carbonates levels in the range of 4% - 10%.
The optimum flotation conditions determined are presented in
Table 10.2.
Table 10.2: Optimum Flotation Conditions
Description |
Value |
Grind |
80% - 75 µm |
Reagents
Dosages – g/t |
- |
Copper
Sulphate |
80 g/t |
Sodium
Ethyl Xanthate |
100 g/t |
Sodium
Carbonate |
200 – 350 g/t |
Starch |
70 – 125 g/t |
XP200
Frother |
35 – 60 g/t |
|
10.3.4 |
Gold Dissolution from Flotation Concentrates |
|
· |
Direct cyanidation of the flotation concentrate resulted in a 27% gold dissolution, |
| // | |
|
· |
Ultra-fine grinding (80% -20 µm) followed by cyanidation and oxygenation resulted in a marginal improvement
in gold dissolution from 27% to 30%, |
|
· |
A single Pressure Oxidation (POX) test was done on concentrate with the main objective to oxidize 100% of
the sulfide which then resulted in a further 98% gold dissolution by cyanidation of the POX leach residue. Formation of Basic Ferric Sulphate
(BFS) resulting in high lime and cyanide consumption in the downstream processing (cyanidation) was observed. A significant amount of
arsenic was also detected in the POX filtrate. |
|
· |
BIOX® of the concentrate provided 99% sulfide decomposition with 97% gold dissolution by cyanidation of
the bio-residue. Formation of iron and cyanide complexes was observed. The solid residue after cyanidation was of the bioleach product
was stable with respect to arsenic. |
Based on the above results, historical test work and consideration
of environmental impacts and risk minimization by adopting commercially established and proven processes, the process route identified
for additional evaluation was flotation, pre-treatment of the concentrate by Bio-oxidation followed by cyanidation.
Variability flotation test work on the ores indicated an average
recovery of 89.2%, a recovery range of 83.4% - 95.9% and recovery standard deviation of 3.4% for Isabella McCays ore and average recovery
of 86.6%, a recovery range of 80.5% - 94.2% and recovery standard deviation of 4.4% for Bubi ore.
|
10.5 |
Pilot Plant Test Work |
The pilot plant test work was conducted over a period of three
months from July 2018 to September 2018, with the follow up laboratory test work being conducted between September 2018 and January 2019.The
pilot plant utilized a total of 20 t of the Isabella McCays ore and 15 t of Bubi ore.
|
10.5.1 |
Pilot Plant Operation and Flowsheets |
The flowsheets evaluated during the pilot plant campaigns are
shown Figure 10.1.
Flowsheet 2 was ultimately adopted as the preferred flowsheet
based on better recoveries and concentrate grades.
Reagent addition was as per optimum flotation conditions outlined
above.
| // | |
Flowsheet
1 |
Flowsheet
2 |
|
|
Figure 10-1: Pilot Plant Campaign Flowsheets
|
10.6.1 |
Recoveries and Mass Pulls |
The Isabella McCays ores gold recoveries ranged from 85.9%
to 91.0% and the mass pulls ranged from 3.8% to 6.0% with a weighted average of 88.4% recovery and 5.0% mass pull. The Bubi ore recoveries
ranged from 85.9% to 88.8% and mass pulls ranged from 7.8% to 15.2% with averages of 87.5% recovery and 10.0% mass pull.
|
10.6.2 |
Chemical Analyses of Bulk Concentrates |
The analyses of the individual and blended concentrates produced
from the pilot plant operation for the BIOX® process piloting was within the limits of the BIOX® process requirements.
|
10.6.3 |
Additional Laboratory Test Work and Simulation |
Due to constraints on the classification circuit, the grind
on the flotation feed ranged from 63% to 68% - 75 µm against a targeted grind of 80% - 75 µm. This outcome was addressed by
conducting additional comparative laboratory flotation tests at these grinds to validate the effect of grind with modelling and simulation
applied to the actual pilot plant recoveries to derive expected recoveries at the target grind as explained in the latter section.
|
10.6.4 |
Flotation Rate and Comparative Grind Tests |
To determine the expected pilot plant recoveries at the target
grind of 80% - 75 µm, comparative flotation rate tests were conducted on the individual ores at the pilot plant grind of 65% - 75
µm and the target grind.
| // | |
The results showed that the target finer grind of 80% - 75 µm
consistently resulted in higher recoveries in comparison to the pilot plant grind of 65% - 75 µm with recovery increments ranging
from 0.2% - 4.7% on all ore types.
|
10.6.5 |
Modelling and Simulation |
|
10.6.5.1 |
Grind and Recoveries |
Eurus Mineral Consultants (EMC) were engaged to review and
conduct modelling and simulation on the laboratory and pilot plant test work results.
The comparative results of the simulated pilot plant recoveries
at 80% - 75 µm and the actual recoveries at 65% - 75 µm are presented in Table 10.3. The results indicate an expected recovery
improvement of 3.1% and 4.2% on the Isabella McCays and Bubi ores with grind improvement from 65% - 75 µm to 80% - 75 µm respectively.
Table 10.3: Comparative Pilot Plant
Simulated Recoveries
Ore
Source |
Head
g/t |
65%
- 75 µm (Pilot Plant) |
80%
- 75 µm (Simulation) |
Var:(80% - 75 µm)
-(65% - 75 µm) |
%
Mass Pull |
Conc
g/t |
%
Rec |
%
Mass Pull |
Conc
g/t |
%
Rec |
%
Mass Pull |
Conc
g/t |
% Rec |
Isabella
North |
2.00 |
4.2 |
41.3 |
86.1 |
4.4 |
40.5 |
89.2 |
0.2 |
-0.8 |
3.1 |
Isabella
South |
2.54 |
5.1 |
45.4 |
90.3 |
5.2 |
44.6 |
92.0 |
0.2 |
-0.8 |
1.7 |
McCays
|
2.20 |
5.5 |
33.7 |
83.7 |
5.9 |
33.3 |
88.8 |
0.4 |
-0.4 |
5.1 |
Isabella
McCays Total* |
2.20 |
4.7 |
41.0 |
86.9 |
4.9 |
40.3 |
90.0 |
0.3 |
-0.7 |
3.1 |
Bubi |
2.59 |
8.7 |
26.0 |
86.9 |
9.2 |
25.6 |
91.1 |
0.6 |
-0.4 |
4.2 |
*Based
on ISBN-50%, ISBS-30%, McCays-20% |
|
10.6.5.2 |
Flotation Residence Times |
The modelling and simulation were also applied to derive requisite
flotation residence times for the proposed Flowsheet 2 (Table 10.4).
Table 10.4: Flotation Residence Times
Flotation
Stage |
Residence
Time-Mins |
Rougher |
84 |
Cleaner |
68 |
Re-Cleaner |
46 |
Cleaner
and Re-Cleaner Scavenger |
55 |
|
10.6.6 |
Projected Operational Gold Recovery |
The following observations from the test work programme results
provide evidence of expected higher operational recoveries than the average expected 90.0% and 91.1% derived for the Isabella McCays and
Bubi ores, respectively.
| // | |
|
· |
Both Isabella McCays and Bubi ores indicated a positive correlation of head grade and recoveries. With pilot
plant head grades being slightly lower than the planned LoM grades, actual plant recoveries can be expected to be better than pilot and
simulated recoveries at the same grind. |
|
· |
Laboratory test work and plant simulation results showed marginal improvement in recoveries ranging from 0.3%
to 0.9% with finer grinding from 80% - 75 µm to 90% - 75 µm. Although marginal and subject to further validation and
analysis of economic benefits, the trend provides a basis for additional optimization prior to implementation or continuous improvement
during the operational phase. |
|
· |
Comparative simulation of the proposed flotation circuit comprised of a Rougher, Cleaner Scavenger and a common
2-stage cleaning and a flowsheet comprising a Rougher, Cleaner Scavenger and separate 2 -stage showed marginal recovery improvement of
0.5% to 0.8% with the latter indicating potential to improve recoveries with flowsheet reconfiguration subject to validation and analysis
of economic benefits. |
|
· |
Statistical analysis of results from all laboratory and pilot plant test work results showed expected recoveries
of 90.2% and 92.1% and recovery ranges of 85.4% - 95.1% and 89.2% - 95.0% at one standard deviation for the Isabella McCays and Bubi ores,
respectively. |
|
10.6.7 |
Improvements in Flotation Gold Recovery |
It is anticipated that with better knowledge of the recovery
relationships, optimal milling and flotation design, steady state operation, higher head grades with continuous improvement and the benefits
of the economies of operating experience, the downside recoveries can be avoided and that the operational recoveries ranging from a minimum
of the expected values of 90.0% and 91.1% for Isabella McCays and Bubi respectively to a maximum of 95.0% for both ores may be realized.
The test work was conducted on ore samples from Isabella McCays
and Bubi deposits to develop test work data to design a gold processing plant. Test Work Results Summary of the test work results is presented
in Table 10.5.
| // | |
Table 10.5: Summary of the Test Work
Pre-Feasibility Results
BIOX®
Test work on Sulfide Concentrate |
|
|
Isabella McCays |
Bubi |
Sulfide
oxidation |
% |
89.6 |
90.0 |
Gold
recovery |
% |
88.8 |
95.7 |
NaCN
consumption |
kg/tconc |
16 - 18 |
18 - 20 |
Lime
consumption |
kg/tconc |
5 - 15 |
5 - 15 |
BIOX® pilot plant test work programs were completed on
composite Isabella McCays and Bubi concentrates produced during the on-site flotation test work programs. The pilot plant programs have
provided details of sulfide oxidation performance under various operating conditions for each concentrate, as well as the relationship
between gold dissolution and sulfide oxidation. This data has been used to specify certain design criteria for a full-scale BIOX®
plant treating both concentrates. Associated metallurgical test work programs focusing on unit processes such as liquid – solids
separation, neutralization and BIOX® product CIL were also completed on slurries generated during each pilot plant campaign.
The Isabella McCays bulk concentrate sample had a gold grade
of 49.9 g/t and a sulfide sulfur grade of 18%. The mineralogical assemblage comprised of 28.5% pyrite, 22.2% arsenopyrite and 0.02% stibnite.
The continuous BIOX® pilot plant operated on this sample for a period of 103 days and the run included detailed sampling phases at
6.5 and 6-day retention times.
The BIOX® test work indicated the following:
|
· |
An average BIOX® sulfide oxidation of 89.6% was achieved at a 6-day retention time and a feed slurry solids
concentration of 20%, |
|
· |
This resulted in an average CIL gold dissolution of 88.8% on the BIOX® product solids, |
|
· |
The lower-than-expected sulfide sulfur oxidation levels in the pilot plant overflow product slurry are believed
to be due to short-circuiting of unoxidized/partially oxidized solids between the reactors, |
|
· |
The BAT BIOX® tests completed on the various Isabella McCays concentrate samples achieved sulfide oxidation
levels in the range 86.4 to 99.3% and yielded gold dissolutions in the range 92.3 to 97.9%. |
The continuous neutralization pilot run conducted on an Isabella
McCays BIOX® liquor sample produced a suitable effluent since the As(T) concentration in the neutralized solution was at 0.5 ppm
and the TCLP testing of the residue showed a final As(T) leachate of <3 ppm, below the stipulated 5 ppm requirement. Continuous neutralization
tests are recommended to optimize the use of the Isabella McCays float tails for Stage 1 pH control with respect to high Fe concentration
in TCLP extract for the batch neutralization tests.
The settling behaviour and flocculent requirement for the various
Isabella McCays process slurries were found to be comparable to projects with a similar concentrate mineralogy previously evaluation during
BIOX® test work programs.
| // | |
The Bubi bulk concentrate sample had a gold grade of 28 g/t
and a sulfide sulfur grade of 27.1%. The mineralogical assemblage comprised of 57.2% pyrite and 9.00% arsenopyrite. The continuous BIOX®
pilot plant operated on this sample for a period of 235 days and the run included detailed sampling phases at 6.5 and 6-day retention
times.
The BIOX® test work indicated the following:
|
· |
An average BIOX® sulfide oxidation of 90% was achieved at a 6.5-day retention time and a feed slurry solids
concentration of 20%, |
|
· |
This resulted in an average Carbon in Leach (CIL) gold dissolution of 95.7% on the BIOX® product solids, |
|
· |
The BAT tests completed on the Bubi concentrate sample achieved sulfide oxidation levels in the range 97 –
98% and yielded gold dissolutions in the range 92.3 to 96.8%. |
The continuous neutralization pilot run conducted on a Bubi
McCays BIOX® liquor sample produced a suitable effluent since the As(T) concentration in the neutralized solution was at 0.5 ppm
and the TCLP testing of the residue showed a final As(T) leachate of < 0.4 ppm, below the stipulated 5 ppm requirement. Continuous
neutralization tests are recommended to optimize the use of Bubi / Isabella McCays float tails for Stage 1 pH with respect to high Fe
concentration in TCLP extract for the batch neutralization test.
The settling behaviour and flocculent requirement for the for
the various Bubi process slurries were found to be comparable to that achieved on the Isabella McCays process slurries. The test work
indicated higher settling area requirement of 4,00 m²/t/h for the Bubi BIOX® product compared the 2,90 m²/t/h for the Isabella
McCays BIOX® product.
The QP is of the opinion that the mineral processing and metallurgical
testing data is adequate for the purposes used in the TRS.
| // | |
|
11 |
MINERAL RESOURCE ESTIMATES |
The MRE was prepared by DRA in terms of the definitions of
S-K 1300.
Leapfrog Geo™ software was used to construct volumetric
solids for the zones of weathering, structural discontinuities, and mineralization. Three-dimensional (3D) resource modelling, using geostatistical
techniques for grade estimation, was done in Datamine Studio RM™. The key assumptions and methodologies used for the mineral resource
estimates are outlined.
A 3D Digital Elevation Model (DEM) was provided by Bilboes
Gold. The points were generated from an airborne photogrammetric survey conducted in 2018 incorporating the existing rock dumps, heap
leach pads, and mining pits. For pits that contained water ingress, a bathymetric survey was done to determine pit bottom.
The database comprised of DD, RC and Percussion (PERC) holes,
summarized in Table 11.1. At Isabella South (ISBS), drill holes dip between 40° and 60° towards the NW. At Isabella North (ISBN),
drill holes dip between 45° and 60° towards the NW/SE while at McCays, they dip at 60°towards the SE. At Bubi, the majority
of drill holes dip at approximately 60° towards the SE.
Table 11.1: Summary of Drill Holes
Property
|
DD
Holes |
RC
Holes |
Perc
Holes |
Total
|
No.
of Holes |
Meters
|
No.
of Holes |
Meters
|
No.
of Holes |
Meters
|
No.
of Holes |
Total
Meters |
ISBS |
68
|
10,233.74
|
72
|
9,636
|
957
|
34,312
|
1,097
|
54,181.74 |
ISBN |
105 |
19,574.97 |
67 |
9,279 |
765 |
34,325 |
937 |
63,179.01 |
BUBI |
68 |
11,500.02 |
90 |
10,376 |
1,663 |
65,532 |
1,821 |
87,408.02 |
McCays |
89 |
12,565.49
|
88 |
8,931 |
298 |
20,055 |
475 |
41,551.49 |
For drilling campaigns prior to 2011, density measurements
were taken at irregular intervals. During the 2011 to 2018 drilling campaigns, every metre of core was sampled, and submitted for density
measurements. The Archimedes method of density measurement was used. A summary of these measurements per project area are presented in
Table 11.2.
| // | |
Table 11.2: Summary of Density Measurement
per Resource Area
Resource
Area |
No
of Measurements |
Minimum
(g/cm3) |
Maximum
(g/cm3) |
Mean
(g/cm3) |
ISBS |
2,599 |
2.01 |
3.39 |
2.76 |
Resource
Area |
No
of Measurements |
Minimum
(g/cm3) |
Maximum
(g/cm3) |
Mean
(g/cm3) |
ISBN |
3,604 |
2.00 |
3.94 |
2.78 |
McCays |
3,967 |
2.18 |
3.93 |
2.8 |
Bubi |
7,152 |
2.25 |
4.65 |
2.83 |
To check the reliability of the density measurements that were
done in-house, 36 samples from Bubi, 25 from ISBS, 25 from ISBN and 15 from McCays were submitted to an independent third-party laboratory
at the Institute of Mining Research, University of Zimbabwe. The in-house measurements compare well with the check analysis.
Mineralization at Bilboes is classified as Archaean hydrothermal
alteration within broad shear zones. Discrete mineralized zones have been observed from the oxide open cast mining. A summary of the mineralized
zone is presented in Table 11.3 and displayed in Figure 14.1.
Table 11.3: Summary of the Geological
Parameters for the Geological Models
Resource
Area |
Strike |
Dip
(°) |
No
of Mineralized zones |
ISBS |
NE |
~65°
to 75° towards the SE |
16 |
ISBN |
NE |
79° to
85° towards the SE |
16 |
Bubi |
NE-SW |
SE at approximately
75° |
10 |
McCays
|
NE-SW |
73°
towards the NW |
16 |
| // | |
ISBS ISBN
| // | |
|
11.5 |
Weathering and Oxidation |
Oxidation profiles are important in determining the different
rock mass densities of ‘ore’ and ‘waste’ and the metallurgical processing method, costs, and recoveries important
during mine planning. The geological models included a transitional zone, as illustrated in purple in Figure 11.1.
Figure 11-1: Section View showing Oxidation
Profile at ISBS
In areas with limited DD or RC drilling, percussion drilling
data was used to inform the mineralized zones during the geological modelling process. Where percussion holes were used for geological
modelling, they were also included in the estimation.
Oxidation of the “ore zones” is a result of chemical
alteration that postdates mineralization. The moderately weathered part of the Transitional Zone was historically mined as part of Oxide
Zone because the two zones were considered economically viable by heap leaching. The weakly weathered material was mined together with
the fresh sulfide ore. For these reasons, the moderately weathered Transitional Zone was estimated together with the Oxide Zone.
All DD and RC samples that occur within a mineralized zone,
irrespective of whether they are located in the Oxide, Transitional, or Sulfide Zone, were used to estimate grade in all three zones.
Percussion samples that occur in the Transitional and Oxide parts of the model, were used to estimate grade in the moderately weathered
Transitional and Oxide parts of the model.
| // | |
For all four properties, the predominant sampling interval
was 0.5 m and 1.0 m; hence a composite length of 1.0 m was used. The statistics for the Au grade before and after compositing were reviewed
to ensure that a bias had not been introduced into the database.
For ISBS, a reliable semi-variogram was obtained for the Castile
Main mineralized zone, because this zone contained the most samples. These variogram model parameters were used for all other zones in
the Castile area (northern part of the project).
For the southern part of the project (Maria area), samples
from these zones were grouped together to increase the number of sample pairs, while paying attention to the across strike direction to
ensure that samples from one zone do not form pairs with samples from another zone.
At Bubi, the Main zone produced a reliable semi-variogram.
All the other zones used these variogram parameters for estimation.
For McCays, a reliable semi-variogram was obtained for Main-1
and footwall West mineralized zones, which occur in fault block 2 and fault block 3, respectively. The variogram obtained within fault
block 2 was applied to all mineralized zones within block 2, similarly the variogram obtained within fault block 3 was used for zones
within that block. For the remaining mineralized zones, the variogram for the mineralized zone with a similar orientation was selected.
Diana Main was the zone that produced a robust semi-variogram
in ISBN and was used for all other mineralized zones within ISBN. Table 11.4 contains the normalized variogram parameters used for the
estimation.
Table 11.4: Variogram Parameters used
for Grade Estimation
Property |
Zone |
Normalized
Variogram Parameters |
Nugget
(Co) |
Spherical
Range 1 |
Spherical Range 2 |
X1 |
Y1 |
Z1 |
C1 |
X2 |
Y2 |
Z2 |
C2 |
ISBS |
Castile
Main |
0.26 |
4.1 |
4.1 |
4.1 |
0.56 |
42 |
42 |
14.2 |
0.19 |
Maria Area |
0.44 |
3.2 |
3.2 |
3.2 |
0.28 |
20.8 |
20.8 |
6.3 |
0.28 |
ISBN |
Diana Main-1 |
0.31 |
17 |
17 |
4 |
0.32 |
36 |
36 |
7 |
0.38 |
Bubi |
Main Zone |
0.32 |
10.6 |
10.6 |
4.1 |
0.41 |
70 |
70 |
12.3 |
0.27 |
McCays |
Main-1 |
0.26 |
4 |
4 |
4 |
0.51 |
30 |
30 |
5 |
0.23 |
FW West |
0.19 |
8 |
8 |
1 |
0.2 |
30 |
30 |
6 |
0.61 |
The top capping strategy considered various criteria to determine
the optimum values.
| // | |
Based on the above criteria, it was determined that Au values
should remain uncapped. Top and bottom capping for density values was however necessary.
|
11.9.1 |
Krige Neighborhood Analysis |
The aim of Krige Neighborhood Analysis is to determine the
optimal theoretical search and estimation parameters during Kriging to achieve an acceptable Kriging Variance and Slope of Regression
whilst ensuring that none or a minimal number of samples are assigned negative Kriging Weights.
The search parameters used are presented in Table 11.5.
The method of estimations for Au was Ordinary Kriging while
density was estimated using Inverse Power of Distance with a Power of 2. Estimations were undertaken using the Estimate process in Datamine.
The boundaries between the waste / ore were treated as hard boundaries. Parental cell estimation was used.
Dynamic Anisotropy was used to search for samples during estimation
to account for the change in dip of the mineralized zones.
| // | |
Table 11.5: Summary of Search Parameters
Project |
Search
Method |
Search
Distance Along Axis (M) |
3-1-3
Rotation Around Axis (°) |
Search
Volume Factor |
Number
of Samples |
S
vol 1 |
S
vol 2 |
S vol 3 |
X (Strike) |
Y (Down-Dip) |
Z (Across
Strike) |
Z (3) |
X (1) |
Z (3) |
S vol
2 |
S vol
3 |
Min |
Max |
Min |
Max |
Min |
Max |
ISBS |
Dynamic Anisotropy
(Rectangular) |
60 |
40 |
6 |
150 |
62 |
0 |
2 |
50 |
24 |
48 |
12 |
60 |
12 |
72 |
ISBN |
Dynamic Anisotropy
(Rectangular) |
70 |
50 |
20 |
140 |
80 |
0 |
1.5 |
5 |
24 |
54 |
20 |
60 |
2 |
72 |
Bubi |
Dynamic Anisotropy
(Rectangular) |
100 |
40 |
20 |
300 |
80 |
0 |
2 |
50 |
24 |
60 |
12 |
60 |
12 |
72 |
McCays |
Dynamic Anisotropy
(Rectangular) |
60 |
60 |
20 |
320 |
78 |
0 |
1.5 |
5 |
6 |
30 |
6 |
30 |
1 |
70 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| // | |
|
11.9.3 |
Block Model Parameters |
The block model parameters are presented in Table 11.6. Sub-cell
splitting was used to ensure that the volumes are adequately represented in the block model. Zonal control was applied during grade estimation
to ensure that samples from one zone were not used to estimate in another zone.
Table 11.6: Block Model Configuration
Field |
Description |
ISBS |
ISBN |
Bubi |
McCays |
XMORIG |
Block
Model Origin X Coordinate |
661,200 |
662,100 |
684,150 |
665,100 |
YMORIG |
Block Model
Origin Y Coordinate |
7,845,850 |
7,847,600 |
7,863,300 |
7,849,200 |
ZMORIG |
Block
Model Origin Z Coordinate |
750 |
690 |
900 |
730 |
XINC |
Parent Block
Dimension in the X direction |
20 |
20 |
20 |
10 |
YINC |
Parent
Block Dimension in the Y direction |
10 |
10 |
10 |
10 |
ZINC |
Parent Block
Dimension in the Z direction |
5 |
5 |
5 |
5 |
NX |
Number
of Parent cells in the X direction |
115 |
92 |
98 |
220 |
NY |
Number of Parent
cells in the Y direction |
180 |
118 |
300 |
190 |
NZ |
Number
of Parent cells in the Z direction |
90 |
112 |
70 |
100 |
Model validation included the following:
|
· |
Visual comparisons of the estimated grades against the composite sample grades, |
|
· |
Statistical comparisons for the mean of estimated grades against the mean of the composited samples, |
|
· |
Trends (or swath analysis checking) to ensure that the regional grade trends from the drill holes were preserved
in the model. The ordinary kriging algorithm calculates the best estimate by minimizing the estimation error (kriging variance). This
results in smoothing of the block estimates, compared to the samples. The objective of this exercise was therefore to ensure that both
regional and local trends were best preserved, |
|
· |
Filtering out the upper and lower deciles of the sample distribution and comparing that to the same for the
estimated blocks. This was to assess whether there was over or under extrapolation. |
The means between sample and model estimates compared favourably.
Block on block analysis (Swath plots) compares local trends
in the samples against model estimates. The approach was to divide the study areas into 50 m* 50 m* 20 m blocks in the X, Y and Z direction
respectively, and to select samples within each block, and compare their mean against the mean of the model. Sample and model mean compared
favourably.
Compared to the October 2021 MRE for the Measured and Indicated
categories, which was prepared in accordance with CIM Standards, there is a 3.1 % decrease in tonnage and 0.8 % decrease in grade. Tonnage
for the Inferred category has decreased by 2.8 %, and the grade has increased by 0.7%. Reasons for the change is due to in-fill grade
control drilling as well as mining depletions.
| // | |
|
11.12 |
Mineral Resource Classification |
Mineral Resource classification used a “Checklist”
approach, where various criteria were considered and rated. These included:
|
· |
Data quality and integrity, |
|
· |
Data spacing for confidence in geological interpretations and grade interpolation, |
|
· |
Confidence in the geological interpretation from a regional and local perspective, and how that interpretation
influences the controls for Au mineralization, |
|
· |
Reliability of the estimate in the mined-out areas, |
|
· |
Geostatistical confidence in grade continuity, |
|
· |
Geostatistical parameters such as kriging variance, kriging efficiency and search distances, to measure the
relative confidence in the block estimates. |
All the above criteria were linked to drill hole spacing as
the minimal qualifier for consideration. Areas with drillholes spacing less than 25 m; blocks estimated with at least 6 drillholes and
with a relative ordinate kriging variance of less than 0.20 were considered for classification of Measured Mineral Resources; areas with
drillholes spacing less than 50 m: blocks estimated with less than 4 drillholes and with a relative ordinary variance of less than 0.3
were considered for classification of Indicated Mineral Resources. Areas with drill hole spacing less than 100 m was considered for Inferred
Mineral Resources. The drill spacing distance buffer was created in Leapfrog Geo™. A checklist used for the assessment of the Mineral
Resources during classification criteria is summarized in Table 11.7.
To determine what qualifies as surface mineable resources,
whittle shells provided by DRA using a gold price of US$2,400/oz were used. The gold price chosen was based on the expectation for the
gold price in 2024. See Table 16.1. Details of the additional Whittle parameters are presented in Table 11.8. Mineral Resources within
these shells were considered to have the potential for eventual economic extraction by open cast mining methods.
| // | |
Table 11.7: Checklist Criteria for Resource
Classification
Items |
Discussion |
Confidence |
Drilling
Techniques |
Diamond drill
holes |
High |
Reverse Circulation
drilling |
Medium |
Percussion
drilling (predominantly in the oxidized zone) |
Low |
Logging |
All drill
holes were logged by qualified geologists using standardized codes. Completed logs are checked and signed off by the senior geologist
prior to capture into the database. The logging was of an appropriate standard for mineral resource estimation. |
High |
Drill
Sample Recovery |
Recoveries
recorded for every core run. |
High |
Sampling
Methods |
Half core
sampled at 1 m intervals for diamond drilling. Sampling occurs wherever there is evidence of alternation. |
High |
Portion of
the rock chips collected at 1 m intervals sampled for RC drilling and Percussion drilling. |
Medium |
Quality
of Assay Data and Laboratory Tests |
An external
independent commercial laboratory has been used for all analytical test work for diamond and RC drilling. Appropriate sample preparations
and assaying procedures have been used. Duplicate samples and industry CRMs were inserted within the sampling stream. The data has been
declared fit for the purposes of geological and mineral resource modelling. |
High |
Percussion
drilling used Bottle-Roll Analysis that was performed in-house. Analytical results are considered of low reliability because the method
can only measure acid soluble gold. |
Low |
Verification
of Sampling and Assaying |
Data integrity
checks performed by DRA and Bilboes have confirmed data reliability. |
High |
Location
of Data Points |
Drill hole
collar location and orientation were surveyed by a qualified surveyor. |
High |
Tonnage
Factors (Density) |
The Archimedes
method of density determination was used in-house. Verification analysis was performed at the University of Zimbabwe and. The comparison
of the in-house density determination and the check analysis compare favorably. |
High |
Data
Density and Distribution |
Diamond and
RC drilling was done at 25 m X 25 m on well informed areas, 50 m X 50 m on moderately informed areas, and 100 m X 100 m on less informed
areas. The level of data density is sufficient to place Mineral Resources into the Measured, Indicated, and Inferred categories, respectively. |
High |
| // | |
Items |
Discussion |
Confidence |
Database
Integrity |
Data
is stored in Datamine™ Fusion Database. |
High |
Geological
Controls on Mineralization |
Geological
setting and mineralization are very well understood. Mineralization is constrained to shear zones within a broad hydrothermal alteration
halo. |
High |
Statistics
and Variography |
Anisotropic
spherical variograms were used to model the spatial continuity for the main mineralization domains. |
Medium |
Top
or Bottom Cuts |
No cutting
was applied to the Au estimation. Top and bottom cuts were applied to the density during estimation. |
High |
Data
Clustering |
Drill holes
were drilled on an approximately regular grid, with decreasing regularization at depths. |
Medium |
Block
Size |
Determined
by QKNA. 20 mE x 10 mN x 20 mRL 3D block model constructed for ISBS, ISBN, and Bubi. For McCays the blocks were 10 mE x 10 mN x 5 mRL. |
High |
Search
Distance |
Determined
with the aid of QKNA as well as drilling spacing. |
High |
Grade
Estimation |
Au estimated
using Ordinary Kriging. Density estimated using Inverse Distance to the power if two. |
High |
Resource
Classification |
Reported
on a checklist bases with the drilling space. |
High |
Metallurgical
Factors |
Metallurgical
parameters were considered during the whittle optimization process, based on comprehensive test work and pilot plant. |
High |
Block
Cut-offs |
0.9 g/t
Au is used for block cut-offs. Other sensitivities at 0.0 g/t, 0.5 g/t and 1.5 g/t Au cut-off have also been presented. |
High |
This MRE was constrained to a Lerchs-Grossmann pit shell
using 0.9 g/t Au as the cut-off grade (Table 11.8). A gold price of US$2,400/oz scenario assessment was also completed to determine surface
infrastructure boundaries to ensure that no potential future resource is sterilized through siting of future infrastructure.
| // | |
Table 11.8: Optimization Parameters
used for the Lerchs-Grossmann Shells
Parameter |
Description |
Unit |
Bubi |
Isabella |
McCays |
Optimization Parameters |
Oxide Slope Angle - Weathered |
Degrees |
30 |
30 |
30 |
Trans Slope Angle |
Degrees |
48 |
48 |
48 |
Fresh Slope Angle |
Degrees |
51/55 |
51/55 |
48/51/55 |
Production Rate |
Ktpm |
180 |
240 |
240 |
Gold Price |
US$/Oz |
2,400 |
2,400 |
2,400 |
Discount Rate |
% |
10.0% |
10.0% |
10.0% |
Mining Costs |
Ore Cost |
US$/t Mined |
3.30 |
3.20 |
3.20 |
Waste Cost |
US$/t Mined |
2.30 |
2.30 |
2.30 |
Fixed Cost and Other |
US$/t Ore |
10.25 |
4.05 |
3.09 |
Processing Costs |
Processing Cost (Sulfide) |
US$/t Treated |
32.81 |
19.02 |
10.02 |
Recovery - Sulfides |
% |
88.90% |
83.60% |
83.60% |
Financial Parameters |
Royalties |
% |
5.00% |
5.00% |
5.00% |
Taxes |
% |
25.00% |
25.00% |
25.00% |
The Mineral Resource Estimate is summarized in the following
table using a cut-off grade of 0.9 g/t Au and constrained inside a Lerchs-Grossman (LG) optimized pit shell using US$ 2,400 per ounce
gold price (Table 16.1). Mineral Resources exclude Mineral Reserves.
The Mineral Resource Estimate is summarized in the following
table using a cut-off grade of 0.9 g/t Au and constrained inside a Lerchs-Grossman (LG) optimized pit shell using US$ 2,400 per ounce
gold Table 11.9.
Base Case Mineral Resources (0.9 g/t Au) Reference Point: in
Situ (31 December 2023)
| // | |
Table 11.9: Mineral Resource based on
a 0.9g/t Au Cut-Off Grade
Property |
Classification |
Tonnage
(Mt) |
Au
(g/t) |
Metal (kg) |
Ounces
(koz) |
ISBS |
Measured |
1.325 |
2.34 |
3,104 |
100 |
Indicated |
5.211 |
2.17 |
11,299 |
363 |
Total Measured and Indicated |
6.537 |
2.20 |
14,403 |
463 |
Inferred |
1.335 |
1.80 |
2,404 |
77 |
ISBN |
Measured |
2.589 |
2.68 |
6,939 |
223 |
Indicated |
4.430 |
2.31 |
10,246 |
329 |
Total Measured and Indicated |
7.019 |
2.45 |
17,186 |
553 |
Inferred |
1.613 |
2.18 |
3,520 |
113 |
Bubi |
Measured |
1.288 |
1.95 |
2,518 |
81 |
Indicated |
14.006 |
2.19 |
30,708 |
987 |
Total Measured and Indicated |
15.294 |
2.17 |
33,225 |
1,068 |
Inferred |
5.116 |
1.8 |
9,208 |
296 |
McCays |
Measured |
0.925 |
3.05 |
2,821 |
91 |
Indicated |
3.874 |
2.37 |
9,193 |
296 |
Total Measured and Indicated |
4.799 |
2.50 |
12,014 |
386 |
Inferred |
1.054 |
2.16 |
2,274 |
73 |
Totals (ISBS + ISBN + Bubi + McCays) |
Total Measured |
6.128 |
2.51 |
15,382 |
495 |
Total Indicated |
27.522 |
2.26 |
61,446 |
1,976 |
Total Measured and Indicated |
33.650 |
2.30 |
76,828 |
2,470 |
Total Inferred |
9.118 |
1.99 |
17,406 |
560 |
| · | S-K 1300 definitions observed for classification of Mineral Resources. |
| · | Mineral Resources are in situ. |
| · | Block bulk density interpolated from specific gravity measurements taken from core samples. |
| · | Resources are constrained by a Lerchs-Grossman (LG) optimized pit shell using Whittle software. |
| · | Mineral Resources are not Mineral Reserves and have no demonstrated economic viability. The estimate of
Mineral Resources may be materially affected by mining, processing, metallurgical, infrastructure, economic, marketing, legal, environmental,
social, and governmental factors (Modifying Factors). |
| // | |
| · | An IA is preliminary in nature, it includes inferred mineral resources that are considered too speculative
geologically to have the economic considerations applied to them that would enable them to be categorized as mineral reserves, and there
is no certainty that the IA will be realized. |
| · | Numbers may not add due to rounding. |
| · | The Mineral Resource Estimate has been depleted to reflect mining up to 31 December 2023. |
| · | Effective Date of Mineral Resource Estimate is 31 December 2023. |
The QP is of the opinion that all issues relating to technical
and economic factors likely to influence the prospect of economic extraction can be resolved with further work.
| // | |
| 12 | MINERAL RESERVE ESTIMATES |
No Mineral Reserve is defined for the Bilboes Project at this
level of study.
| // | |
| 13.1 | Hydrological and Geotechnical Investigation |
Little was known of the hydrogeology for either the Isabella-McCays
or Bubi Mines. There are some hydrogeological boreholes drilled around the Isabella-McCays pits, however there are no existing records
for these boreholes, therefore no historical water levels or groundwater quality baseline could be determined.
The only levels measured and recorded are related to the geotechnical
boreholes drilled around the Isabella-McCays and the Bubi open pits, where packer-testing was performed.
The estimation of an initial general hydraulic head over the
entire area was done using the correlation between the elevation and hydraulic head values measured in each of the geotechnical boreholes.
Nine geotechnical boreholes were selected for packer testing.
The interval selection was based on the presence of discontinuities determined on the televiewer log along the borehole interval.
The results of the packer testing have been incorporated in
the numerical model.
| 13.1.2 | Conclusion and Recommendations |
The numerical simulation for Isabella – McCays Mines
and Bubi Mine lead to the following conclusion that each model indicates that a cone of drawdown will develop as a result of the mining
activities. The open pits simulated act as hydrogeological sinks and groundwater inflows into the open pits will need to be pumped out
for the duration of mining. After mining activities stop, the groundwater levels start to recover due to the formation of the pit lakes
and the decrease of the hydraulic gradients towards the open pits.
The following shows the maximum drawdown at the end of mining
and the recovery of the groundwater levels vs. time (Table 13.1)
Table 13.1: Isabella – McCays
– Bubi – Predicted drawdown vs. time
Isabella - McCays drawdown vs. time |
|
Bubi drawdown vs. time |
Year |
Max. Drawdown (m) |
Year |
Max. Drawdown (m) |
7 |
112 |
6 |
85 |
25 |
43 |
25 |
77 |
50 |
33 |
50 |
45 |
75 |
21 |
75 |
10 |
100 |
13 |
100 |
9 |
Following the geotechnical logging of the drill holes, the
following major rock domains were encountered (Table 13.2).
| // | |
Table 13.2: Percentage Rock Types at
Different Mining Pits
Rock Type |
|
Percentage Rock (%) |
|
Isabella South |
Isabella North |
McCays |
Bubi |
Arkose |
26 |
14 |
- |
- |
Chlorite Schist |
23 |
- |
- |
- |
Schist |
16 |
- |
- |
- |
Felsic Schist |
35 |
83 |
- |
- |
Mafic Schist |
- |
2 |
21 |
13 |
Meta-Basalt |
- |
1 |
65 |
28 |
Banded-Iron Formation (BIF) / Chert |
- |
- |
4 |
- |
Meta-Andesite |
- |
- |
10 |
55 |
Saprock |
- |
- |
- |
4 |
| 13.2 | Rock Mass Classification |
The rock mass quality for the different Bilboes pits (Isabella
South, Isabella North, McCays and Bubi) was assessed using the Rock Mass Rating (RMR) RMR89 classification system developed by Bieniawski
(1976, 1989). The results of the rock assessments show that the rock mass for all the four mining pits is considered to be fair to good.
| 13.3 | Geotechnical Conclusions and Recommendations |
Based on the analysis of the engineering geological aspects
of the investigated deposits which included rock mass characterization, hydrogeology, intact rock properties and structural geology, a
geotechnical model comprising design parameters was developed. Using these design parameters; kinematic, empirical and limit equilibrium
analysis was conducted to determine the optimal slope configuration for the various deposits.
Based on the analysis conducted, it is understood that the
capacity of the slopes should be affected by the following:
| · | Completely weathered slopes should be a maximum of 3 m in height, and it is recommended that the material
is pushed back from the crest, |
| · | For the transitional rock (highly to moderately weathered), by a combination of rock mass strength and
adverse structural orientation. Inter-ramp heights of 60 m are achievable with inter-ramp angles between 45° and 50°, |
| · | For the unweather rock slopes adverse structural orientation should determine the slope angle which is
achievable. Inter-ramp heights of 90 m are achievable with inter-ramp angles of between 50° and 55°, depending on the wall direction. |
The controls on slope design are listed for the Bilboes pits
with comments on the reliability of the data and descriptions of how the design issues were addressed for the purposes of the slope design
(Table 13.3).
| // | |
Table 13.3: Slope Design
Slope Design Issue |
Confidence |
Mitigation |
Faulting
Faults were inferred to be sub-vertical; however, the width of fractured
/ disturbed ground either side of the faults is not understood. |
Moderate |
Kinematics was used to assess the stability of inter-ramp and overall slope. Inter-ramp and slope angles are restricted to between 50 and 55° and 45 to 50° respectively to ensure subvertical faults do not daylight |
Rock Fabric
Large amounts of structural data were collected, defining the local occurrence,
intensity, and orientation (dip and dip
direction) of the structures |
High |
Good practice to collect and expand on the structural data collected to ensure that unknown structures are defined |
Soil and Intact Rock Properties
Intact samples of rocks were collected and tested. |
Moderate |
Good practice to have an ongoing soil and rock testing program to build on the database |
Rock Mass Characterization
Rock mass characterization was conducted and generally is representative
of rock mass conditions. |
High |
Rock mass characterization should be ongoing to expand on the rock mass database. |
Groundwater
The groundwater studies were conducted by SLR and included in the limit
equilibrium analysis |
High |
All excess water inflows can be sent to local PCDs and then used as process water make up. |
The detailed pit slope design should require the following
phasing once a final pit shell and pit stages are defined and inter-related.
| · | Additional intact strength testing is required for the rock and soil formations, |
| · | Additional structural data needs to be collected from the pits using a televiewer, |
| · | Continual collection of rock mass data from drilled core, |
| · | Conducting of additional stability analysis using the new pit shells, generated from with recommended
slope angles recommendations presented on this document, and the revised geological and geotechnical models, |
| · | Developing the Ground Control Management Plan, |
| · | Projecting major structures onto the pit Phases and final pit for geotechnical review and development
of remedial measures and the timing of their implementation as required, |
| · | Defining the locations of the initial vibrating wire piezometers, the initial prisms, survey stations
and trial horizontal drains and their specifications and the target dates for their installations. |
The Bilboes Project consists of four mining areas containing
between one to three pits each. These areas are McCays, Isabella South, Isabella North and Bubi as shown in Figure 13.1 and Figure 13.2.
| // | |
Figure 13-1: Block Plan Showing
Bilboes Pits and Process Plant Location
Figure 13-2: Block Plan Showing
Bilboes Pits Location
| // | |
The LoM schedule considers the blending requirement that a
maximum of 50% of feed to plant be sourced from Isabella North and the remainder from Isabella South (preferred blend) or McCays.
| · | A mining contractor will be used for all open pit mining related earthmoving activities. |
| · | All deposits will be mined utilizing conventional truck and shovel method. |
| · | Transitional and fresh materials and waste will be drilled and blasted. |
| · | Free dig and blasted waste will be loaded, hauled with 60 tonne haul trucks and dumped to designated waste
dump locations which will be systematically dozed and levelled to allow dump to be raised to design heights. |
| · | Free dig and blasted materials will be loaded and hauled with 40 or 60 tonne haul trucks to the plant
feed RoM pad. There it will either be directly tipped into the crushing facility or placed on the RoM pad stockpile areas. |
In this IA the previous Base Case was revalidated with Phase
1 being a 240 ktpm gold processing plant treating ROM material from Isabella and McCays (after a short ramp-up period) before being upgraded
for a Phase 2 to treat ROM material from the Bubi pit at 180 ktpm.
SLR were engaged to investigate a new concept design and associated
costing based on a Phased paddock approach for base case. The objectives were to minimize initial capital outlay and delay further expenditure
according to a three-Phase build programme that aligned with the LoM production schedule.
| 13.6 | Whittle Optimization Input Parameters |
A summary of the input parameters for the Whittle Pit optimization
are presented in the section. This will define the ultimate pit limit and optimize the scheduling of the mining sequence, ensuring the
economic viability of the pit.
| 13.6.1 | Financial Parameters |
The financial parameters used in the pit optimization are summarized
in Table 13.4
Table 13.4: Whittle Optimization Input
Parameters: Financial Parameters
Financial Parameters for Net Commodity Price |
Unit |
US$ 1,950 |
US$ 1,650 |
US$ 1,800 |
Date of Information: |
March 2023 |
High Case |
Low Case |
Base Case |
Base Currency |
US$ |
0 |
0 |
0 |
Annual Discount Rate (%) |
(%) |
10.0% |
10.0% |
10.0% |
Commodity Price |
US$/oz |
1,950 |
1,650 |
1,800 |
Royalties |
(%) |
5% |
5% |
5% |
Refining Cost (% of Commodity Price) |
% |
1.0% |
1.0% |
1.0% |
Total Selling Cost |
US$/oz |
117.00 |
99.00 |
108.00 |
Financial Parameters for Net Commodity Price |
Unit |
US$ 1,950 |
US$ 1,650 |
US$ 1,800 |
|
|
|
|
|
Net Commodity Price |
US$/g |
58.93 |
49.87 |
54.40 |
| // | |
| 13.6.2 | Geotechnical and General Parameters |
The geotechnical and general input parameters used in the pit
optimization are summarized in Table 13.5.
Table 13.5: Whittle Optimization Input
Parameters: Geotechnical and General Parameters
Geotechnical Parameters |
Unit |
Value |
Value |
Value |
Value |
Primary Zone |
|
ISBN |
ISBS |
McCays |
Bubi |
Inter-Ramp Slope Angle |
|
|
|
|
|
Oxide |
Degrees |
30 |
30 |
30 |
30 |
Trans |
Degrees |
48 |
48 |
48 |
48 |
Fresh |
Degrees |
51/55 |
51/55 |
48/51/55 |
51/55 |
Geotechnical Parameters |
Unit |
Value |
Value |
Value |
Value |
Bench Face Slope Angle |
|
|
|
|
|
Oxide |
Degrees |
55 |
55 |
55 |
55 |
Trans |
Degrees |
90 |
90 |
90 |
90 |
Fresh |
Degrees |
90 |
90 |
90 |
90 |
Ramp Specifications – 60t truck |
|
|
|
|
|
Single Lane Width |
m |
12.5 |
12.5 |
12.5 |
12.5 |
Dual Lane Width |
m |
18.6 |
18.6 |
18.6 |
18.6 |
Design gradient (%) |
(%) |
10% |
10% |
10% |
10% |
Dilution and Mining Recovery |
Unit |
Value |
Value |
Value |
Value |
Mining Dilution |
(%) |
4% |
4% |
4% |
4% |
Mining Recovery |
(%) |
95% |
95% |
95% |
95% |
Distance ex-pit to Plant |
km |
2.5 |
3.5 |
2.6 |
28 |
Mining Cost Parameters |
Unit |
Value |
Value |
Value |
Value |
Reference Level Elevation (RL) |
RL |
1,151 |
1,135 |
1,163 |
1,195 |
Mining Cost Adjustment Factor (MCAF) |
US$/vert. meter |
0.006 |
0.006 |
0.006 |
0.006 |
| // | |
| 13.6.3 | Waste Rock Cost - Mining |
Different waste mining costs were used in Whittle for each
production tonnage scenario. This was done to emulate the impact of fixed G&A costs on the overall cost per tonne of rock mined.
The waste mining cost for Base Case is shown in Table 13.6.
Table 13.6: Whittle Optimization Input
Parameters: Waste Mining Cost
Waste Mining Cost - Primary Zone |
Units |
ISBN |
ISBS |
McCays |
Bubi |
Oxide - free dig |
US$/tonne |
2.10 |
2.10 |
2.10 |
2.33 |
Trans and Fresh - including drill and blast – 240 (180) ktpm |
US$/tonne |
2.68 |
2.68 |
2.68 |
3.03 |
| 13.6.4 | Process Plant Throughput |
Similarly to the waste mining cost, different costs were used
for rock fed to plant (PF). Due to the reduced confidence by the Bilboes Owner’s team, all oxide mineralized material was reclassified
as waste rock, mined, and discarded as such. The Whittle input parameters for Base Case is shown in Table 13.7.
Table 13.7: Process Plant Throughput
Mining Cost Parameters |
Unit |
ISBN |
ISBS |
McCays |
Bubi |
Total Plant Feed Mining Cost |
US$/tonne |
|
|
|
|
Trans and Fresh – 240(180) ktpm |
US$/tonne |
3.50 |
3.50 |
3.50 |
3.95 |
Extra Plant Feed Mining Cost (haul cost to plant) |
US$/tonne |
|
|
|
|
Mining Cost Parameters |
Unit |
ISBN |
ISBS |
McCays |
Bubi |
Trans and Fresh – 240(180) ktpm |
US$/tonne |
1.00 |
1.40 |
1.04 |
9.24 |
Mill throughput Requirement |
|
|
|
|
|
LoM throughput Requirement – 240 (180) ktpm |
Mtpa |
2.88 |
2.88 |
2.88 |
2.16 |
Processing Cost Parameters |
Unit |
Value |
Value |
Value |
Value |
Processing Cost Base |
|
|
|
|
|
Trans and Fresh – 240(180) ktpm |
US$/tonne |
19.86 |
19.86 |
19.86 |
35.65 |
GA's – 240(180) ktpm |
US$/tonne |
2.59 |
2.59 |
2.59 |
3.46 |
Total Processing Cost |
|
|
|
|
|
Trans and Fresh – 240 (180) ktpm |
US$/tonne |
22.45 |
22.45 |
22.45 |
39.11 |
Whittle Processing Cost |
|
|
|
|
|
Trans and Fresh – 240 (180) ktpm |
US$/tonne |
23.45 |
23.85 |
23.49 |
48.35 |
Process Recovery |
|
|
|
|
|
Trans and Fresh - BIOX & CIL Mean Recovery |
(%) |
83.6 |
83.6 |
83.6 |
88.9 |
| // | |
| 13.7 | Plant Feed Dilution and Plant Feed Loss |
Dilution of 4% and mining losses of 5% were assumed as the
plant feed domains and are continuous and will be clearly delineated and marked. Sampling of blast holes would be the basis for grade
control in this analysis. The accuracy of the resulting plant feed/waste boundary is limited by the resolution of the grade control, which
is a function of the density of the drilling pattern. The lower the flitch height, the smaller the pattern, the smaller the distance between
“plant feed holes” and “waste holes” and hence the smaller the potential for plant feed loss/ plant feed dilution.
These dilution and loss percentages are accepted as being in line with smaller flitch heights, such as the 5 m flitches associated with
this mining operation. The Bilboes team has many years of experience in mining the various pit oxide rock and believes that the transitional
and fresh plant feed will be more easily visually identifiable for grade control drilling and selective mining.
| 13.8 | Whittle Optimization Results |
The results of the Whittle optimization are presented in Table
13.8.
| // | |
Table 13.8: Whittle Optimization Results
All Run Results Max Profit |
Abb |
Units |
US$ 1,800 |
US$ 1,950 |
US$ 1,650 |
Parameter |
|
|
5% loss & 4% dilution |
|
O-P Discounted Cashflow |
|
US$M |
847.9 |
1,012.2 |
684.0 |
Life of Mine |
LoM |
Year |
9.2 |
10.0 |
8.4 |
Mineable Inventory |
PF |
Mt |
23.3 |
25.2 |
21.5 |
Measured & indicated |
PF |
Mt |
23.3 |
25.2 |
21.5 |
All Run Results Max Profit |
Abb |
Units |
US$ 1,800 |
US$ 1,950 |
US$ 1,650 |
Inferred |
PF |
Mt |
0.0 |
0.0 |
0.0 |
Unclassified |
PF |
Mt |
0.0 |
0.0 |
0.0 |
Mineable Inventory |
Waste |
Mt |
201.3 |
220.8 |
184.0 |
Strip Ratio |
SR |
tw:tpf |
8.63 |
8.76 |
8.56 |
Head grade |
Au |
g/t |
2.38 |
2.33 |
2.44 |
Au Recovery |
Au |
% |
85.9% |
85.9% |
85.9% |
Au Metal Recovered |
Au |
kg |
47,718 |
50,369 |
45,065 |
Measured & indicated |
Au |
kg |
47,718 |
50,369 |
45,065 |
Au Metal Recovered |
Au |
oz |
1,534,185 |
1,619,389 |
1,448,866 |
EBIT before CAPEX |
|
US$M |
1,036 |
1,259 |
825 |
| // | |
| 13.9 | Whittle Production Schedule Results |
The resultant production schedule results for the optimized
IA production for the Base Case, is summarized in Figure 13.3 and Figure 13.4. The LoM schedule considers the blending requirement that
a maximum of 50% of feed to plant be sourced from Isabella North and the remainder from Isabella South (preferred blend) or McCays. Irregular
waste production profiles were smoothed to ensure the production profile is practically implementable.
Figure 13-3: Base Case Production
Schedule 240/180 ktpm - Plant Feed Grade
Figure 13-4: Base Case Production
Schedule 240/180 ktpm - Gold Ounces
| 13.10 | Sensitivity analysis |
Two production scenarios were also tested to try to reduce
the capital cost of the project.
| 13.10.1 | Scenario 80 ktpm then 60 ktpm Bubi |
This scenario looked at an initial production of 80 ktpm with
a standalone 80 ktpm plant which was not designed to allow further expansion.
| // | |
This was considered the smallest Phase 1 “start-up”
plant module, with material being sourced from Isabella and McCays, providing an even lower initial capital option. The mining plan initially
targeted 80 ktpm from McCays, followed by blending the feed with material from Isabellas’ and then mining 60 ktpm from Bubi. This
option aimed at the lowest initial capital cost possible.
13.10.2
Scenario 80 ktpm then 160 ktpm then 120tpm Bubi
This scenario looked at doubling up of initial production to
160 ktpm with a modular plant to achieve a throughput of 160 ktpm process capacity. The mining plan initially targeted McCays, followed
by blending the feed with material from Isabellas and then Bubi at a reduced rate of 120 ktpm. This option aimed at the lowest initial
capital cost, followed by higher production from Year seven onwards.
| // | |
Table 13.9 presents the results from some of the scenarios
tested.
Table 13.9: Sensitivity Results
Parameter
|
Abb
|
Units
|
Base
Case |
Scenario
80/60 ktpm |
Scenario
80/160/120 ktpm |
Gold
Price |
GP
|
US$/oz
|
US$
1,800 |
US$
1,950 |
US$
1,650 |
US$
1,800 |
US$
1,950 |
US$
1,650 |
US$
1,800 |
US$
1,950 |
US$ 1,650 |
Production
Rate |
PR
|
Ktpm
|
240ktpm
/ 180ktpm Bubi |
80ktpm
– 60ktpm Bubi |
80 - 160 - 120ktpm |
Discounted
Cashflow |
DCF
|
US$
m |
847.9
|
1,012.20
|
684
|
478.8
|
563.5
|
390.3
|
593.1
|
712
|
486.9 |
Life
of Mine |
LoM
|
Year
|
9.2
|
10
|
8.4
|
27.4
|
29.8
|
25
|
18.2
|
19.8
|
16.5 |
Mineable
Inventory |
Ore
|
Mt
|
23.3
|
25.2
|
21.5
|
23.1
|
25
|
21.2
|
23.1
|
25
|
21.2 |
Measured
& Indicated |
Ore
|
Mt
|
23.3
|
25.2
|
21.5
|
23.1
|
25
|
21.2
|
23.1
|
25
|
21.2 |
Mineable
Inventory |
Waste
|
Mt
|
201.3
|
220.8
|
184
|
198.3
|
217.7
|
180
|
198.3
|
217.7
|
180 |
Strip
Ratio |
SR
|
t:t
|
8.63
|
8.76
|
8.56
|
8.59
|
8.7
|
8.48
|
8.59
|
8.7
|
8.48 |
Head
grade |
HG
|
g/t
|
2.38
|
2.33
|
2.44
|
2.39
|
2.33
|
2.45
|
2.39
|
2.33
|
2.45 |
Au
Recovery |
Au
|
%
|
85.90%
|
85.90%
|
85.90%
|
85.90%
|
86.00%
|
85.90%
|
85.90%
|
86.00%
|
85.90% |
Au
Metal Recovered |
Au
|
kg
|
47,718
|
50,369
|
45,065
|
47,395
|
50,102
|
44,641
|
47,395
|
50,102
|
44,641 |
Measured
& Indicated |
Au
|
kg
|
47,718
|
50,369
|
45,065
|
47,395
|
50,102
|
44,641
|
47,395
|
50,102
|
44,641 |
Au
Metal Recovered |
Au
|
koz
|
1,534.19
|
1,619.39
|
1,448.87
|
1,523.79
|
1,610.80
|
1,435.23
|
1,523.79
|
1,610.80
|
1,435.23 |
| // | |
| 13.12 | Mining Contractor Production Costs |
The resultant production costs for the optimized IA production
trade-offs for Base Case240 ktpm - 80 ktpm are summarized in Table 13.10.
Table 13.10: Adjudicated Mining Contractor
Cost
All Run Results Max Profit |
Abb |
Units |
US$ 1,800 |
US$ 1,950 |
US$ 1,650 |
Parameter |
|
|
5% loss & 4% dilution |
|
O-P Discounted Cashflow |
|
US$M |
847.9 |
1,012.2 |
684.0 |
Life of Mine |
LoM |
Year |
9.2 |
10.0 |
8.4 |
Mineable Inventory |
PF |
Mt |
23.3 |
25.2 |
21.5 |
Measured & indicated |
PF |
Mt |
23.3 |
25.2 |
21.5 |
All Run Results Max Profit |
Abb |
Units |
US$ 1,800 |
US$ 1,950 |
US$ 1,650 |
Inferred |
PF |
Mt |
0.0 |
0.0 |
0.0 |
Unclassified |
PF |
Mt |
0.0 |
0.0 |
0.0 |
Mineable Inventory |
Waste |
Mt |
201.3 |
220.8 |
184.0 |
Strip Ratio |
SR |
tw:tpf |
8.63 |
8.76 |
8.56 |
Head grade |
Au |
g/t |
2.38 |
2.33 |
2.44 |
Au Recovery |
Au |
% |
85.9% |
85.9% |
85.9% |
Au Metal Recovered |
Au |
kg |
47,718 |
50,369 |
45,065 |
Measured & indicated |
Au |
kg |
47,718 |
50,369 |
45,065 |
Au Metal Recovered |
Au |
oz |
1,534,185 |
1,619,389 |
1,448,866 |
EBIT before CAPEX |
|
US$M |
1,036 |
1,259 |
825 |
| 13.12.1 | Production Fleets Required |
The scheduling is driven by the excavating capability during
each period (i.e. the product of the number of excavators and their productivity).
For scheduling purposes, it was assumed that 100t excavators
with 6 m3 bucket will be deployed on waste and 75t excavators (4 m3 bucket) on plant feed. These excavators will
be loading trucks with a payload capacity of 60 tonnes and 40 tonnes respectively. The first principal productivity calculations for determining
period by period material movement were based on Caterpillar 390, Caterpillar 374 excavators and Caterpillar 773 dump trucks and Caterpillar
740 articulated dump trucks respectively.
The Waste Rock Dumps (WRD) were staged appropriately to minimize
haul distances throughout the LoM.
| // | |
The WRD construction and final landform are based on the following
criteria:
| · | The maximum height of waste dumps is currently set at 40 m above ground level. |
| · | A swell and re-compaction factor of 30% was utilized to calculate a material placement density of waste
on the waste dumps. |
| · | Dump bench face angle is designed at 30° during construction, with 10 m berms separating benches.
During the rehabilitation Phase, the WRD side slopes will be progressively dozed down into continuous slopes without benches, as required
for agricultural use. After rehabilitation, the final landform slope will not exceed 19° overall slope angle. |
| · | The waste dumps will be built with a minimum 1:100 gradient on the top surface to ensure effective water
shedding. |
| · | All dump locations were selected outside the boundaries as indicated by the Whittle gold price scenario
of US$ 2400/oz. Future prospecting zones were also considered so as not to sterilize any potential resource. |
| · | The minimum operating width on the waste dump is 40 m. |
| · | All the waste dumps were designed with ramps of 10% gradient. |
| · | It has been assumed that all waste is benign and does not require any neutralizing treatment, or containment. |
| // | |
| 14 | PROCESSING AND RECOVERY METHODS |
| 14.1 | Process Test work Results |
Extensive test work (Section 13) has been undertaken. The plant
feed (fresh sulphide) is refractory to normal free milling processing due to the ultrafine gold particles being largely encapsulated (and
generally appearing in solid solution) within the sulphide minerals. As a result, the selected process encompasses a biological sulphide
destruction step (Outotec proprietary BIOX® process) to liberate the gold particles and allow dissolution by a cyanide solution in
the CIL circuit. The test work results were used to derive the Process Design Criteria (PDC) for the processing plant as depicted in Table
14.1.
Table 14.1: Process Plant Design Criteria
Description |
Unit |
Design |
Remarks |
Plant Annual RoM Throughput |
|
|
|
Phase 1 Isabella McCays |
tpa |
2,880,000 |
Years approx. 1-6 |
Phase 2 Bubi |
tpa |
2,160,000 |
Years approx. 6-10 |
Plant Monthly RoM Throughput |
|
|
|
Phase 1 Isabella McCays |
tpm |
240,000 |
|
Phase 2 Bubi |
tpm |
180,000 |
|
Head Grade Analysis |
|
|
|
Transitional plant feed Gold |
|
|
|
Isabella Mc Cays |
g/t |
1.94 |
Average |
Bubi |
g/t |
1.61 |
Average |
Sulphides plant feed Gold |
|
|
|
Isabella McCays |
g/t |
2.42 |
Average |
Bubi |
g/t |
2.42 |
Average |
Ore Characteristics |
|
|
|
Density |
|
|
|
Isabella McCays |
t/m³ |
2.77 |
Average |
Bubi |
t/m³ |
2.85 |
|
BBWi (Bond ball work index) |
|
|
|
Isabella McCays |
kWh/t |
17.00 |
Average |
Bubi |
kWh/t |
21.45 |
|
Ore Product Sizes |
|
|
|
Crushed plant feed (P80) (80% passing size) |
mm |
13 |
|
Milled plant feed (P80) (80% passing size) |
microns |
75 |
|
Flotation Mass Pull |
|
|
|
Isabella McCays |
% |
5 |
|
Bubi |
% |
10 |
|
| // | |
| 14.2 | Process Flow Description |
Plant feed will be derived from two main mining areas, namely
Isabella McCays and Bubi, with production throughput to be Phased over the LoM based on tonnage, proximity to the process plant and metallurgical
characteristics. Bubi plant feed, destined to be processed over the latter part of the LoM will be trucked approximately 23 km to the
processing plant which will be situated at the Isabella McCays complex. The envisaged phasing is as depicted in Figure 14.1 Table 14.1.
Operations in the process plant can essentially be divided
into seven main sections. Comminution (plant feed size reduction by crushing and milling to facilitate liberation of the mineral particles
for subsequent downstream concentration),
| · | Flotation (concentration of sulphides and gold into a small concentrate mass), |
| · | Biological oxidation - BIOX® (destruction of the sulphides in the concentrate using oxidizing bacteria
to expose the gold particles for downstream recovery), |
| · | Carbon in leach (cyanidation leach of the BIOX® residue and recovery of the solubilized gold onto
activated carbon), |
| · | Electrowinning and smelting, |
| // | |
Figure 14-1: Bilboes Simplified
Process Flow Diagram
The crusher circuit has been designed to process the full LoM
design monthly tonnage (240 ktpm ISBM). When processing Bubi plant feed to the crushing circuit monthly throughput will reduce to approximately
180 ktpm due to the harder nature of the Bubi plant feed. Plant feed with a top size of approximately 900 mm is received from the open
pit mining operations at the RoM Pad by haul truck. The plant feed may be stockpiled on the RoM Pad (for blending or delayed feeding purposes)
or directly tipped into the primary jaw crusher. The crusher circuit comprises primary jaw and secondary cone stages to produce a product
with P80 of 30 mm for stockpiling on the crushed plant feed stockpile ahead of the milling circuit. Total capacity of the crushed plant
feed stockpile is approximately 26 kt with a live capacity of 8 kt (24 hours). In times of plant feed shortages, the excess stockpile
capacity may be processed using dozers and loaders to feed through the crushed plant feed stockpile chutes.
| 14.2.1.2 | Milling and Classification |
The crushed plant feed is withdrawn from beneath the crushed
plant feed stockpile and fed onto the mill feed conveyor by vibratory feeders. The mill feed conveyor discharges directly into the single
ROM Ball Mill feed hopper.
| // | |
The conveyor is fitted with a weightometer to measure the throughput
as well as controlling the speed of the vibratory feeder to give the set tonnage to the mill. The ball mill is a grated discharge mill
with steel liners and utilizing steel balls as the grinding media.
Milled slurry discharges via a trommel screen into the mill
discharge sump and is pumped to the cyclone classification circuit. The cyclone overflow containing the fine particles gravitates to the
flotation conditioning tank in the flotation section. The coarse particles exit in the cyclone underflow stream and return to the ball
mill. Product size from the milling section is 80% passing 75 μm. During processing of the Bubi plant feed monthly milling throughput
will reduce to 180 ktpm due to the harder nature of the Bubi plant feed.
Cyclone overflow from the milling section discharges into the
flotation conditioning tank where it is adjusted with process water to the set flotation feed density. Flotation reagents are also added
in this tank and the slurry is allowed to condition for a set period prior to being pumped to the flotation cells. The circuit will operate
at natural pH and be configured in a rougher, cleaner, recleaner and cleaner scavenger format to facilitate maximum gold and sulphide
recoveries while minimizing the carbonate recovery to the concentrate. Sodium Ethyl Xanthate (SEX) is used as the collector for the sulphide
minerals, copper sulfate as an activator for the sulphide minerals while starch and sodium carbonate are used as depressants for the carbonates.
The rougher tails, forming the tailings product, are dewatered in the water recovery thickener circuit, and pumped to the flotation tailings
storage facility. The recleaner concentrate forms the concentrate and is pumped to the concentrate thickener for dewatering ahead of processing
in the biological oxidation section. Supernatant water from the tailings and concentrate thickeners is recycled to the milling and flotation
sections. The supernatant solution is recycled back to the process plant.
| 14.2.3 | Biological Oxidation (BIOX®) |
In the BIOX® section bacterial oxidation of the sulphide
minerals occurs, (by mesophilic bacteria, operating in the range of 15°C – 45°C) resulting in liberation of the included
gold particles for further downstream recovery.
| 14.2.3.1 | Biological Leaching |
Dewatered flotation concentrate is pumped to the BIOX®
surge tank where it is diluted to the required density of approximately 18% solids. The slurry is then fed to the primary reactors (in
parallel), with slurry overflowing to the secondary reactors (in series). Oxygen and carbon dioxide (air), nutrients, defoamer and sulfuric
acid are added to the tanks. The required bacteria cultures are contained within the tanks; oxygen, solids feed rate, pH and temperature
control are essential to ensure the bacterial activity level is maintained. Bacterial oxidation of the sulphides optimally takes place
at a pH of 1.5 - 2.2 and a temperature of approximately 42oC. As the concentrate contains a relatively high amount of carbonate
the addition of sulfuric acid will be required to maintain the required pH. Temperature is maintained by the circulation of cooling water
via cooling coils within the reactors. Aeration of the tanks (oxygen supply) is by medium pressure air blowers (240 kPa). Air hold-up
in the tanks is approximately 17% of live volume. Total required residence time in the reactors is 6.5 days.
The oxidized slurry product exits the final Stage 2 reactor
and is pumped to the Counter Current Decantation (CCD) section for separation of the acidic liquid and oxidized solids components.
| // | |
| 14.2.3.2 | Counter Current Decantation |
A three stage CCD (counter current decantation) circuit allows
for removal of the acidic solution components from the oxidized solids. The thickener underflow solids are progressively washed of acidic
solution in an up-flow manner from Thickener 1 to 3, exiting as Thickener 3 underflow, while the acidic solution is progressively concentrated
in a down flow manner exiting as Thickener 1 overflow. Make up water is added to the feed of Thickener 3 to maximize the washing efficiency.
The Thickener 3 underflow slurry (washed oxidized product) is pumped to the CIL section for final gold recovery, while the Thickener 1
overflow acidic solution is pumped to the neutralization section for precipitation of the acidic and other acidic deleterious components.
The neutralization circuit comprises eight stages, where the
acidic solution is initially neutralized to a pH of approximately 4.5 with limestone (Stage 3) and then to a pH of 7 (Stage 7) with lime.
The acidic components and solubilized arsenic are precipitated to the various sulfates with the arsenic fixed insolubly as basic ferric
arsenate. The slurry is pumped to the water recovery thickener, where it combines with flotation tails, where the solids are dewatered
(thickener underflow) and thereafter pumped to the Flotation tailings storage facility. The supernatant thickener overflow solution is
channelled to the process water circuit for recycling to the process plant in general. Residence time per neutralization stage (8 off)
is 1.5 hours thereby resulting in a circuit residence time of 12 hours.
Washed oxidized slurry from the neutralization section is pumped
to the pre-leach tank (CIL Tank 1) of the CIL circuit, where the slurry will be subjected pH adjustment with lime and additional aeration
to ensure complete oxidation of cyanide consumers. The slurry will then overflow to CIL Tank 2 where cyanide is added and from there down
the circuit to the final CIL tank. Tanks 2 to the final tank all contain activated carbon, retained within the tank by an interstage screen.
Slurry residence time in the circuit is set at 36 hours, by which time maximum gold dissolution will have occurred and the carbon will
have adsorbed approximately 99% of the soluble gold. The exiting slurry from the final CIL tank will pass over a carbon safety screen
to ensure no loss of carbon due to possible interstage screen perforations, before gravitating to the tailings surge tank. From here the
slurry is pumped to the detoxification circuit for cyanide destruction before being pumped into the BIOX® tailings storage facility.
The carbon within the CIL tanks is pumped counter currently to the slurry flow, together with the relevant slurry, upstream from the last
CIL tank to the CIL Tank 2. The carbon Au value increases as it progresses upstream in the circuit while the slurry solids and liquids
Au values decrease as the slurry flows downstream in the circuit. Loaded carbon is recovered from CIL Tank 2 by pumping the carbon / slurry
to the Loaded Carbon Screen. The slurry passes through the screen and returns to CIL Tank 2. The loaded carbon discharges from the screen
into a hopper from where it is transferred the Acid Treatment Vessel at the head of the carbon treatment circuit.
A loaded carbon batch (5 t) is treated at ambient temperature
with a 3% hydrochloric acid solution for approximately 1 hour in the acid wash vessel to remove inorganic foulants, predominantly calcium,
ahead of the elution process. At the end of the process the spent acid is washed from the column with water and pumped to the BIOX®
tailings tank and ultimately sent to the BIOX® tailings storage facility.
| // | |
The acid washed carbon is transferred by water eduction to
the elution column ahead of desorption of the Au. The elution process is the split Anglo American Research Laboratory (AARL) type. This
process separates the elution (desorption) cycle from the electrowinning cycle thereby adding flexibility to the process. The loaded carbon
is pre-soaked at 110°C with a solution comprising 1% cyanide and 2% caustic soda solution for approximately 1 hour. After this the
carbon is eluted with high quality water at 125°C for a period of approximately 4 hours. The gold bearing solution (preg solution)
is stored in the Preg Solution Tank in readiness for gold recovery in the electrowinning section. For flexibility, a second preg solution
tank is installed to allow fully independent electrowinning to take place. The total elution cycle (including acid treatment) takes approximately
10 hours. The barren carbon is transferred by water eduction from the elution column to the regeneration kiln feed hopper.
The Regeneration Kiln is a horizontal retort type, operating
at a temperature of 750°C (hot zone) in a non-oxidizing atmosphere to prevent ignition of the carbon. In this process organic foulants
such as oils, greases and flotation reagents are removed thus returning the carbon close to its original virgin activity in readiness
for reuse in the CIL circuit. Carbon discharges the kiln into a quench tank (cold water filled) and is then recycled by eductor back to
the CIL circuit.
| 14.2.6 | Electrowinning and Smelting |
The pregnant solution is pumped to the electrowinning circuit
(situated in the Gold Room), comprising two electrowinning cells, each with 16 cathodes and 18 anodes. The cathode is stainless steel
mesh wrapped around a stainless-steel frame, connected to the negative terminal, and encapsulated in a non-conducting, perforated cathode
box. The anode comprises a stainless-steel perforated plate connected to the positive terminal. DC power to each cell is supplied by a
dedicated rectifier (2,000 amps). The preg solution is circulated through the electrowinning circuit over 12 hours. Au in the preg solution
deposits onto the stainless-steel mesh in the cathode box with the generation of hydrogen gas (resulting in localized acidic conditions
in the cell). The pH in the preg solution must be maintained at approximately 13 to prevent excessive corrosion of the stainless-steel
anode due to localized low pH. Oxidation reactions at the anode result in the generation of ammonia and hydrogen amongst others. The gases
are vented off in a very diluted form to the atmosphere via an extraction system. Once the residual Au value in the preg solution has
reached the low setpoint the process is deemed to be complete and is halted.
The cathode boxes are removed periodically from the electrowinning
cell and the gold recovered from the stainless-steel mesh by high pressure water jets. The gold is then filtered and dried in a drying
oven.
The dried gold is mixed with fluxes (generally borax, silica,
and sodium carbonate) and melted in a single pot diesel fired furnace at a temperature of approximately 1,100°C. (Melting
point of gold is 1,064°C). Once molten the gold is poured into Molds, cooled, cleaned, stamped, and stored in the vault
awaiting dispatch to the refinery.
Tailings from the CIL circuit are detoxified to reduce the
Weak Acid Dissociable Cyanide (WAD) levels to below 50 ppm prior to discharge to the BIOX® tailings
TSF. This is accomplished using the INCO SO2 / Air-process. The process requires a copper catalyst, added as CuSO4
(copper sulfate). The SO2 source is Sodium Meta Bisulfite (SMBS), while oxygen is generally sourced from compressed air. Minimum
O2 requirement is generally 1 ppm - 2 ppm. Optimum pH is 8 - 10. The process results in the generation of sulfuric acid and
thus requires the addition of lime (generally) or caustic soda to maintain pH at the optimum level.
| // | |
| 14.3 | Plant Water Requirements |
Raw water will be supplied to the raw water storage tank, with
a live capacity of 2,560 m³, from the pit dewatering pumps and several borehole pumps. The raw water is used for gland service, carbon
transfer duties, elution, gravity concentrator circuit water, reagent make-up and fire service duties. The raw water storage tank will
have a reserve for firefighting purposes. This reserve will be maintained by suitability positioned fire water and raw water pump suctions.
Process water is stored in the process water dam, an earthen
lined structure with a live volume of 10,400 m³. The process water dam collects water from the water recovery thickener, flotation
tailings TSF and any plant run-off from pollution control dams. Process water is supplied to all sections of the plant for hosing and
screen spraying and specifically to the milling and flotation sections for slurry dilution purposes. The process water balance is negative
and relies on a make-up volume (from raw water) of approximately 4,000 m³/day under Phase 2 conditions.
The Bilboes plant will use a substantial number of chemical
reagents / commodities due to its complexity (Table 14.2). Limestone will be sourced locally; all the other reagents will require importation
into Zimbabwe.
| // | |
Table 14.2: Process Plant Major Reagents
/ Commodities
Reagent / Commodity |
Delivery Form |
Area(s) of Use |
Make up Facilities |
Quick / Burnt lime
CaO (85%) |
Bulk powder,
-1 mm solids |
Milling, BIOX®
Neutralization,
CIL, Cyanide
Detoxification |
Bulk Slaking (Hydration)plant supplying hydrated lime – Ca (OH)2 - via a ring main system |
Limestone
(CaCO3) (45%) |
Bulk crushed,
-40 mm solids |
BIOX®
Neutralization |
Milling plant with dedicated supply to neutralization area |
Flocculant (various) |
Dry powder,
25 kg bags |
Flotation tails thickener,
Flotation Conc. thickener,
BIOX® CCD thickeners, Water recovery thickener |
Dedicated batch make up occulant plants
at each relevant site supplying liquid fl |
Flotation Collector: Sodium Ethyl Xanthate
(SEX) |
Dry pellets,
850 kg bulk bags |
Flotation |
Dedicated batch make up plant supplying
liquid reagent |
Flotation Activator
Copper Sulfate (CuSO4) |
Dry powder,
25 kg bags |
Flotation |
Dedicated batch make up plant supplying
liquid reagent |
Flotation Frother |
Dry powder,
200 kg drums |
Flotation |
Dedicated batch make up plant supplying
liquid reagent |
Reagent / Commodity |
Delivery Form |
Area(s) of Use |
Make up Facilities |
Flotation Depressant 1
Sodium Carbonate
(Na2CO3) |
Dry powder,
25 kg bags |
Flotation |
Dedicated batch make up plant supplying liquid
reagent |
Flotation Depressant 2
Starch |
Dry powder,
25 kg bags |
Flotation |
Dedicated batch make up plant supplying liquid
reagent |
Sulfuric Acid |
Bulk tanker liquid 93% H2SO4 |
BIOX® |
Ring main system feeding from storage tank to BIOX® circuit. |
BIOX® Nutrients |
Dry powder,
25 kg bags |
BIOX® |
Dedicated batch make up plant supplying liquid
reagent |
Sodium Cyanide
NaCN |
Briquettes, bulk
1,000 kg bags |
CIL, Elution |
Solution make-up and storage facility |
Caustic Soda
NaOH |
Pellets, bulk
1,000 kg bags |
Carbon
Treatment,
Cyanide make-up
facility |
Solution make-up, storage and distribution facility |
Hydrochloric Acid
HCl |
33% Liquid,
200 l plastic drums |
Carbon
Treatment Acid
Wash |
Direct pumping from drum into Acid Wash solution make up tank |
| // | |
Sodium Metabisulfite
Na2S2O5 |
Powder,
1,000 kg bulk bags |
Cyanide
Detoxification |
Solution make-up, storage and distribution facility |
Diesel |
Bulk Tanker |
Fire water system, Elution and Gold Room |
Local diesel storage tank for distribution |
Milling grinding media
80 mm dia. forged Cr-Mo steel |
200 l steel drums |
Milling |
Ball loader onto Mill feed conveyor |
| // | |
The mine layout is shown in Table 18-1 and Figure 18-2.
Figure 15-1: Mine Layout
Figure 15-2: Overall Site Plan
| // | |
| 15.1 | Geotechnical Investigation and Design |
The Bilboes Project geotechnical engineering investigation
involved the investigation for the Open Pit, TSF, the Process Plant (Plant) and WRD foundation material analysis - Field Investigation
and Data Collation
SLR Rock Engineers visited the site at various stages of the
geological drilling campaign during 2018 which included, review of geological and geotechnical data, geotechnical logging of core and
the collection of intact rock samples for laboratory testing.
Prior to the field investigation, a site reconnaissance study
was conducted, during which the site was assessed with the view to planning the investigation methodology. This was followed by a desktop
study investigation which involved the compilation and assessment of available information on the site including geology, aerial photography,
and previous investigations on the site, where available.
The test pit locations were selected based on early conceptual
site layouts of the TSF, RWD and Plant Site to gain maximum coverage of the area.
Selected soil samples were retrieved from the test pits and
were submitted to the Contech Geotechnical Testing laboratory in Harare, Zimbabwe. The samples were chosen to determine the design parameters
of each material units encountered at the site.
| 15.1.1 | Tailings Storage Facility Site |
The following soil and rock properties were derived from the
investigation and are recommended for use in design, slope stability analysis and seepage modelling (Table 15.1).
Table 15.1: Proposed Soil and Rock Properties
for Foundation Modelling on the TSF Site
Geotechnical
Domain |
Depth
(m) [mean values] |
USCS
|
Dry Density (kg/m3)
|
v
|
Confined Modulus (MPa)
|
Effective Cohesion (KPa)
|
Effective
Friction Angle (°) |
Ksat
(m/s) |
Topsoil
|
0.0
- 0.6 |
CL |
1,700
|
0.3
|
4 |
0 |
27 |
1 x 106 |
Residual
Arkose |
0.6
- 1.0 |
CL/SC/GC
|
1,700
|
0.3
|
8 |
0 |
27 |
1 x 106 |
Residual
Andesite |
0.4
- 1.0 |
CL/SC
|
1,800
|
0.3
|
15 |
0 |
30 |
1 x 106 |
Residual
Meta-Basalt |
0.1
- 0.6 |
CL/SC/GC
|
1,800
|
0.3
|
8 |
0 |
30 |
1 x 106 |
Rock
Type |
Depth
(m) [mean values] |
Rock
Classification |
Dry
Density (kg/m3) |
v |
GSI
|
Rock
Strength (MPa) |
Confined
Modulus (KPa) |
Ksat (m/s) |
Arkose
/ Andesite / Meta-Basalt |
1.0
- 2.0 |
Poor
Quality Rock Mass |
2,600
|
0.4
|
25
- 35 |
1
- 5 |
50
|
1 x 108 |
| // | |
The following soil and rock properties were derived from the
investigation and are recommended for use in plant siting and foundation design (Table 15.2).
Table 15.2: Proposed Soil and Rock Properties
for Foundation Modelling on Process Plant Site
Geotechnical
Domain |
Depth (m)
[mean values] |
USCS
|
Dry
Density (kg/m3)
|
V
|
Confined
Modulus
(MPa) |
Effective
Cohesion
(KPa) |
Effective Friction
Angle (°) |
Topsoil
|
0.0
- 0.4 |
|
Not considered suitable
for founding |
|
Residual
Arkose |
0.4
- 1.0 |
CL
|
1,700
|
2
|
|
0
|
27 |
Residual Arkose -
Medium Dense to
Dense |
1.0
- 1.3 |
CL/SC/GC
|
1,800
|
0.3
|
8
|
0
|
30 |
Rock
Type |
Depth (m)
[mean values] |
Rock
Classification |
Dry
Density (kg/m3) |
V
|
GSI
|
Rock
Strength
(MPa) |
Confined
Modulus
(KPa) |
Arkose
|
1.3
|
Poor
Quality Rock Mass |
2,600
|
0.4
|
25
- 35 |
1-5
|
50 |
| 15.1.3 | Waste Rock Dump Sites |
The Waste Rock Dumps classifies geotechnically as a Class II
Low Hazard.
| · | Waste Rock Dump lift heights should be limited to 10 m with a minimum of a 10 m berm, with an overall
height of 40 m. |
| 15.2 | Civil Engineering and Earthworks |
The general approach adopted was to design/measure and quantify
elements, identified as major capital expenses, from the compiled infrastructure layout drawings, and to make the necessary estimation
for the following items.
| · | Haul road (± 26 km) between Isabella and Bubi, |
| · | Internal mining haul roads for Isabella and Bubi, between the proposed open pit mining access and RoM
handling facilities, |
| · | Mine access roads to the proposed mining infrastructure including road to the Plant, Administration and
Village terraces, Lime stockpile terrace, Substation terrace and existing mine infrastructure, |
| · | Service roads to the PCD, RWD and the relocated Explosive Magazines, |
| · | Re-alignment of a public gravel road around the McCays extension, |
| · | Internal plant roads, bus drop-off and parking, |
| // | |
| · | Raw water pipeline from the wellfields supply to the Plant Process Water Dam, |
| · | Return water pipelines from the TSF to Plant PCD, |
| · | Bulk earthworks for terraces at Isabella including the Plant, RoM tip ramp and platform, |
| · | Substation, Village, Administration, Lime stockpile, Contractor’s Laydown terrace and the RoM transfer
terrace at Bubi, |
| · | Relocation of existing Explosives Magazines at Isabella and Bubi, |
| · | Brake test ramp for the Contractor’s Laydown terrace, |
| · | Mine Village and Administration building layout, |
| · | Sewer reticulation and Wastewater Treatment Works for the Plant, Administration and Village, |
| · | Fire and Potable water reticulation for the Plant, Administration and Village, |
| · | Stormwater channels for the Plant, Administration and Village, |
| · | Process Water Dam at the Plant, |
| · | PDC, provided for the Plant and Administration, as well as the Contractors Laydown, |
| · | Process Plant including the RoM tip, Primary Crusher, Secondary Crusher, Screening building, Transfer
Towers, Floatation Concentrates Thickener, Cooling Towers, Neutralization Tanks, Reactors, BIOX® Area, Flotation, Reagents Area, Gold
Room, |
| · | Leaching Area, Mill Structure, Tailing’s area, Conveyors, Water reticulation, Sewer reticulation,
Buildings. |
| 15.3 | Mechanical Engineering |
The mechanical design criteria cover the process plant and
mining related equipment and is based on established technology and practices in the gold mining and processing industry.
Engineering aspects will be developed and optimized for clear
definition of scope for the project. Mechanical equipment design shall be based on the application of established technology and practices
in the gold mining and processing industry. Equipment will be designed and selected on a “fit for purpose” basis, to carry
out required duties over the LoM period.
Mining and process plant equipment and infrastructure will
be designed for LoM, of. approximately 15 years.
Mechanized and automated methods shall be implemented where
there is a clear contribution to a safer, more productive, and less labor-intensive environment.
| // | |
Total life cycle costing of equipment and processes over "LoM”
shall be considered during design and equipment selection Phase.
Engineering design will endeavor to address outcomes of risk
assessments and HAZOP studies. Resulting designs, selected equipment and processes shall be safe for operating and maintenance by personnel
and shall be eco-friendly.
Value improving initiatives will be undertaken through application
of practical value engineering techniques and the philosophy of standardization and rationalization of equipment (to reduce spares holding
requirements). Design to capacity and process simplification will be applied where possible.
| 15.4 | Electrical Power Supply and Reticulation (including Communications) |
| 15.4.1 | Interconnection to National Grid |
Power will be supplied from the Zimbabwe National Grid by constructing
a 70 km 132 kV Lynx line from Shangani Substation. To feed the line, a line bay will be constructed at Shangani. A mine substation will
be constructed at Isabella. The estimate received is for a 132-kV substation, equipped with a 50 MVA 132/33 kV step-down transformer.
Detailed design should be considered to reduce the secondary
voltage to 11 kV to enable the MV motors to be fed directly without an additional 33/11 kV transformer. The 1.5 MVA required by Bubi can
also be supplied at 11 kV.
Power factor correction will be done with 11 kV capacitors.
Interfaces with other designs occur at the following battery
limits:
| · | Zimbabwe Electricity Transmission and Distribution Company (ZETDC), |
| · | The bulk electricity supply for the project is being planned to cater for a production rate of 508 tph
ROM. This corresponds to an electrical load of up to 34 MVA. |
The connected and anticipated running power demand of the mine
and plant can be seen in Table 15.3 which compares the installed and anticipated running power and lists the estimated running maximum
demand.
Table 15.3: Substation Loading
|
Installed Power (kW) |
Run Power (kW) |
Estimated Maximum Demand (kVA) |
Mills and other 11 kV motors |
22,360 |
18,836 |
19,220 |
Plant LV Load |
18,960 |
13,858 |
14,146 |
Infrastructure |
1,700 |
1,700 |
2,205 |
Total |
43,020 |
34,394 |
35,571 |
| // | |
Four 2.5 MVA emergency power generator sets will be installed
and connected to the 11 kV consumer substation. Emergency power is reticulated to downstream substations at 11 kV, where it is distributed
to the Motor Control Centre (MCCs).
| 15.5 | General Infrastructure |
Table 15.4 lists the building infrastructure that was considered.
Table 15.4: Building Infrastructure
Building |
Type |
Size (m2) |
Security and Access Control |
Prefabricated building |
170 |
Admin Building |
A prefabricated building. Office furniture has been included in the square meter rate. |
430 |
Plant Laboratory |
A prefabricated building. Typical laboratory equipment has been included in the square meter rate. |
540 |
Control Room |
Prefabricated building |
170 |
Change house/s |
Prefabricated building/s |
325 |
Stores |
Two conventionally constructed buildings (brick and mortar) |
220 and 100 |
General Workshop |
A conventional constructed building (brick and mortar) |
520 |
Crusher Workshop |
Conventional constructed building (brick and mortar) |
270 |
Electrowinning and Gold Room |
Conventional constructed building (brick and mortar) |
220 |
Building |
Type |
Size (m2) |
Crusher MCC |
Prefabricated building |
302 |
CIL MCCs |
Prefabricated buildings |
253 |
Floatation MCC |
Prefabricated building |
65 |
Substation |
Prefabricated building |
351 |
Return Water Dam Pumphouses |
Two conventionally constructed buildings (brick and mortar) |
38 |
| 15.6 | Water Management Infrastructure |
The stormwater collection dams, and the pollution control dams
as proposed herein, were designed in compliance with the IFC Environmental, Health and Safety (EHS) Guidelines for Mining (2007), together
with the applicable local Zimbabwean Standards.
| // | |
The project site falls within the Bembezi river sub-catchment
which drains north towards the Zambezi River. The Bembezi river sub-catchment forms part of the Gwayi catchment which largely comprises
the Northern Matabeleland area of hydrological zone A.
The stormwater management plan was developed to comply primarily
with the IFC EHS
Guidelines for Mining (2007); while ensuring adherence to all
the applicable local Zimbabwean Standards namely: the Environmental Management Act (Chapter 20:27) implemented by the EMA of Zimbabwe;
and the Zimbabwe National Water Act (Chapter 20:24) implemented by the Zimbabwe National Water Authority (ZINWA) through the Zimbabwe
National Water Authority Act (Chapter 20:25). In developing the conceptual stormwater management plan, reference was also made to regulation
GN 704 of the South African National Water Act, 1998 (Act No. 36 of 1998).
Daily and monthly rainfall were obtained from the ZMSD Nkayi
Stations over 38 years of hydrological records (from 1980 to June 2018) and were analyzed to understand the long-term monthly averages,
minimum and maximum monthly rainfall. The MAP adopted for this project is 657 mm.
A site wide monthly static water balance model was developed
for the Bilboes operation to establish the storage sizes of the pollution control systems; and the average wet, dry season and average
monthly water balance.
The water balance simulated water re-use associated with the
processing plant, as a pump rate out of the PCD for each of the two mining phases.
The steady state water balance analysis indicates that the
Bilboes flotation circuit requires on average approximately 250 m3/hr (6,015.6 m3/day) during Phase 1 before decreasing
to 201.3 m3/hr (4,854.0 m3/day) in Phase 2. For the steady state water balance analysis, there is no make-up water
required for the BIOX® circuit in all phases of mining.
To improve the understanding of the movement and the status
of the water storage and transport infrastructure elements on the mine and how these changes in response to the varying climatic conditions,
a Dynamic Daily Time Step Water Balance analysis was conducted for the project.
The daily time step water balance analysis for the RWD capacity
of 380,000 m³, a return water pumping rate of 490 m³/hr and a worst-case tailings deposition rate of 240 ktpm yielded only two
major spillages in a 70-year period which is considered to be in line with the IFC Environmental, Health and Safety guidelines for stormwater
collection dams.
Groundwater numerical modelling was undertaken to simulate
the mining operation at Bubi Isabella McCays and the related establishment of the TSF at Isabella McCays. The objective of the modelling
is to determine the potential impact on the groundwater flow and groundwater quality during and post mining, for Isabella McCays and Bubi.
Isabella McCays and Bubi are located 32 km apart, and therefore a separate groundwater model was developed for each site.
The cone of drawdown predicted for both mines show that after
100 years of simulation, both pits will present a residual drawdown of approximately 10 m. However, the extent of each cone of drawdown
is decreasing in time and will remain within the boundaries of the mine sites.
| // | |
The mass transport simulations indicate that a liner is necessary
to contain the migration of the contaminant plume from the contaminant sources.
Waterborne sewage networks have been allowed at the Process
plant, Admin area, Residential Village and Contractor area at Isabella McCays. All areas mentioned above will gravitate to a central sewage
purification plant. The purification plant was designed and costed for 400 people at 150 litres per person per day. The purification plant
will be a vendor supply package.
Phase 1 of the project is to be executed initially mostly at
Isabella McCays and will involve the engineering, detailed design, procurement, construction, and commissioning of a 240 ktpm gold plant
and associated infrastructure.
Phase 2 of the project involves mining at Bubi and a step change
in production to 180 ktpm, due to the higher mass pull expected from the different type of ore. Phase 2 will only commence later in November
2028 to suit the life of mine production schedule.
| 15.8.2 | Engineering and Design |
It has been advocated that a short Front End Engineering Design
(FEED) Phase be implemented to bridge any gaps arising from the Prefeasibility Study (PFS) and Detailed Engineering period. The FEED Phase
will allow detailed design scoping to be done and focus on the key requirements for procurement planning and management.
| 15.8.3 | Construction Philosophy |
The EPCM Contractor will mobilize a Project Construction Management
Team who, under the overall direction of the EPCM Project Manager, through the EPCM Construction Manager will manage and co-ordinate the
activities of the appointed construction contractors.
These appointed construction contractors will perform the construction
operations for the duration of the construction Phase.
The schedule is used for long term planning, including cash
flow. The schedule will be revised to be aligned with the latest information available before the project can be progressed from the planning
Phase to the execution Phase.
| 15.9 | Tailings Storage Facility |
SLR Consulting (Africa) (Pty) Ltd (SLR) were appointed to design
and cost a new TSF and the associated sundry infrastructure which include RWD, silt traps, pollution control system, access roads and
perimeter fencing.
| // | |
It is understood that there are no specific Zimbabwean regulations
or standards that are applicable to TSF designs. The Bilboes TSF design complies with various international regulations, standards, and
guidelines as well as the necessary supplementary Zimbabwean regulations e.g., the environmental protection associated with the disposal
of mining waste, the Zimbabwe Statutory Instrument 6 of 2007 applied and The Zimbabwe Standard Specification for Hazardous Waste Management
(ZWS 806:2012).
According to Bilboes Gold, the Zimbabwe EMA views the incorporation
of a 1.5 mm thick HDPE geomembrane in the lining system as minimum best practice. Caledonia Mining is not a member of the ICMM, or an
official signatory of the Global Industry Standard on Tailings Management (GISTM) but has taken the decision to align its tailings design
and management with the principles of the GISTM. As such, the GISTM principles, as well as other tailings dam standards such as SANS 10286
and ANCOLD (2012) will be taken into consideration in the project development process.
It is understood that the flotation and BIOX® CIL tailings
streams are chemically and physically diverse, and as a result, it was considered appropriate to design a facility with two separate compartments.
The general area for a TSF site was preselected by Bilboes
Gold. SLR conducted a trade-off study that compared various TSF construction, development, and deposition techniques over several TSF
layout options on the pre-selected site area. The trade-off costing exercise demonstrated that the lowest start-up and sustaining capital
costs were associated with a hybrid development system that incorporated full containment of tailings during the initial high Rate of
Rise (RoR) deposition phases, followed by upstream development in the latter phases of development when the RoR reduces to the permissible
2 m/year.
Conventional tailings slurry disposal by way of spigotting
with a maximum allowable RoR of 2 m/year above the containment wall crest was adopted for the project.
EPCM supplied the tailings production profile indicating three
distinct phases of production as presented in Table 15.5.
| // | |
Table 15.5: Production Profile
Phase |
Year |
Deposition Rate (tpm) |
Cumulative Tonnage (t) |
Flotation Tailings |
BIOX® Tailings |
Flotation Tailings |
BIOX® Tailings |
Phase 1 |
1.75 to 7.25 |
240,000 |
12,000 |
14,977,000 |
803,000 |
Phase |
Year |
Deposition Rate (tpm) |
Cumulative Tonnage (t) |
Flotation Tailings |
BIOX® Tailings |
Flotation Tailings |
BIOX® Tailings |
Phase 2 |
7.25 to 13 |
180,000 |
18,000 |
11,178,000 |
1,242,000 |
|
|
|
TOTAL |
28,549,000 |
2,171,000 |
Based on the production profile and plant process data supplied
by DRA, the TSF was sized to accommodate a deposition rate of 28.5 Mt for the flotation tailings compartment, and 2.2 Mt for the BIOX®
compartment.
TSF sizing was further based on an overall downstream (outer)
embankment slope of 1V:4H which is considered an environmentally stable slope to encourage indigenous vegetation growth.
The properties derived from the geotechnical site investigation
and were used for stability analysis and TSF foundation design:
· |
Selected embankment fill material friction angle (Φ’) |
|
: 25°. |
· |
Selected embankment fill material cohesion (C’) |
|
: 25°. |
· |
Selected embankment fill material unit weight |
|
: 20 KPa |
· |
Waste Rock friction angle (Φ’) |
|
: 1,600 kg/m³ |
· |
Waste Rock friction angle (Φ’) |
|
: 35°. |
· |
Waste Rock cohesion (C’) |
|
: 5 KPa |
· |
Waste Rock unit weight |
|
: 2,100 kg/m³ |
· |
Foundation material (residual arkose / andesite) friction angle (Φ’) |
|
: 30° |
· |
Foundation material (residual arkose / andesite) cohesion (C’) |
|
: 12.5 KPa |
· |
Foundation material (residual arkose / andesite) unit weight |
|
: 1,700 kg/m³ |
· |
Bedrock friction angle (Φ) |
|
: 50° |
· |
Bedrock cohesion (C’) |
|
: 50 KPa |
· |
Bedrock unit weight |
|
: 2,600 kg/m³ |
| // | |
| 15.9.3 | Tailings Physical Characterization |
A full suite of geotechnical laboratory tests including foundation
indicator tests, consolidated undrained triaxial tests, slurry settling tests, volumetric shrinkage tests, dispersiveness tests, evaporation/air-drying
tests were conducted on representative Isabella McCays composite and the Bubi flotation tailings samples provided by Bilboes from the
on-site pilot plant. The Isabella McCays composite sample was blended at the Isabella-North: Isabella-South: McCays ratio of 50%: 30%:
20% in line with the mining plan.
The following tailings physical properties were derived from
the geotechnical site investigation and were used in the design of the Bilboes TSF:
· |
In-situ dry density of deposited tailings for capacity calculations |
|
: 1,35 t/m³ |
· |
Flotation tailings solids concentration in slurry (by mass) |
|
: 40% |
· |
BIOX® tailings solids concentration in slurry (by mass) |
|
: 20% |
· |
Flotation tailings specific gravity |
|
2,70 |
· |
BIOX® tailings specific gravity |
|
: 2,75 |
· |
Flotation tailings slurry density |
|
: 1,337 t/m³ |
· |
BIOX® tailings slurry density |
|
: 1,144 t/m³ |
· |
Flotation and BIOX® tailings effective friction angle (Φ’) |
|
: 31° |
· |
Flotation and BIOX® tailings cohesion (C’ (KPa) |
|
: 0 |
· |
Flotation and BIOX® tailings unit weight (kg/m³) |
|
: 1,500 |
Against expectation, the Isabella McCays BIOX® tailings
foundation indicator tests results showed a very fine uniformly graded material (99% passing 0.075 mm sieve).
Based on preliminary discussions with Bilboes regarding the
tailings Particle Size Distribution (PSD), the design envisaged a hybrid system of TSF construction incorporating full wall containment
using waste rock material during the initial stages of deposition (up to Year 7), together with upstream wall raises using dried consolidated
tailings from Year 7 onwards. However, safe upstream construction will not be achievable using such fine tailings, and as such BIOX®
tailings may require full containment. The Isabella McCays BIOX® tailings PSD will therefore need further testing and confirmation
during the detailed design phase.
Based on the XRF results for the Isabella McCays BIOX®
material, the Zimbabwe Standard Specification for Hazardous Waste Management (ZWS 806:2012) prescribes the following liner system as the
minimum liner required for the Bilboes BIOX® tailings:
The design presented in this report is based on the following
selected liner systems (Table 15.6).
| // | |
Table 15.6: Liner System
Layer Description |
Flotation Tailings |
BIOX Tailings |
TSF |
RWD |
TSF |
RWD |
HDPE geomembrane thickness |
1.5 mm |
2 mm |
2 mm |
2 mm |
Base layers |
300 mm selected clayey material (compacted in 2x150 mm thick
layers) |
300 mm compacted clay liner compacted in 2x150 mm thick layers) |
600 mm compacted clay liner compacted in 4x150 mm thick layers) |
600 mm compacted clay liner compacted in 4x150 mm thick layers) |
In-situ base preparation |
Rip and re-compact 150 mm in-situ layer |
Rip and re-compact 150 mm in-situ layer |
Rip and re-compact 150 mm in-situ layer |
Rip and re-compact 150 mm in-situ layer |
For the flotation compartment, the above only applies up to 200 m into the basin. The central portion of the flotation compartment will be lined with CCL as described below: |
|
N/A |
Flotation Compartment Central Portion of Basin Liner |
1 |
600 mm CCL |
2 |
150 mm Base preparation |
| 15.9.5 | Seepage / Leakage Quality |
The geochemical assessment report also provides expected seepage
and liner leakage water qualities following source term modelling.
The geochemical assessment indicated that the BIOX® tailings
are likely to be Potentially Acid Generating (PAG) whilst the flotation tailings are non-PAG.
| 15.9.6 | Contaminant Plume Modelling |
Using the results of the geochemical assessment and source
term modelling of tailings, SLR further conducted contaminant plume modelling to determine plume extents because of seepage or leakage
from the TSF and associated RWDs.
The composite liner option is expected to confine plume migration
to the TSF site with the plume not expected to exceed 260 m from the source over a 100-year period.
| // | |
The TSF complex development incorporates an outer containment
wall, constructed in stages using approved available mine waste and developed in a downstream manner and sized to fully contain all deposited
tailings up to the point when the tailings deposition rate reduces from 240 ktpm to 180 ktpm. The remainder of the facility up to the
LoM will then be raised progressively with upstream wall raises using compacted tailings.
| 15.9.8 | TSF Hazard Classification |
The Bilboes TSF hazard classification was conducted in accordance
with both SANS 10286:1998 and ANCOLD (2012). Based on the assessment the Bilboes TSF can be classified as follows:
| ‒ | A “High” hazard facility per the SANS 10286:1998 safety classification criteria, |
| ‒ | A “High B” consequence category per ANCOLD (2012). |
| 15.9.9 | TSF Operation and Monitoring |
During the life of the TSF, various elements should be monitored
to ensure the integrity of the TSF complex. Monitoring elements will typically include:
| ‒ | TSF engineering parameters, |
| ‒ | Groundwater monitoring programme, |
| ‒ | Dust monitoring programme. |
| 15.9.10 | TSF Closure Concept |
The closure concept is envisaged to include a covering of the
mine waste with a low hydraulic conductivity layer such as a clay or geosynthetic membrane. There will be on-going rehabilitation of the
TSF complex through on-going vegetating of the embankment slopes.
An optimization of the previous TSF was undertaken by SLR Consulting.
All previously determined design criteria, including site location, plant processes, tailings production, deposition methodology, tailing
material characteristics as well as earthworks and embankment construction methodology were assumed.
| · | The assumption is that the currently selected site is fixed. Due to the topographical constraints of the
current site, a large volume sacrificial wall needs to be constructed for the TSF Phase 1 deposition, which could be reduced if an alternative
site is found. |
| · | The IA LoM production profiles were provided by DRA (240 ktpm): |
| ‒ | The total tonnes expected are 23.1 Mt: |
| ‒ | Flotation TSF compartment: 22.9 Mt. |
| ‒ | BIOX TSF compartment: 1.7 Mt |
| ‒ | The total LoM is 10 years. |
| // | |
| · | The maximum allowable RoR, for this IA, was assumed to be 2.5 m/year, to lower the starter wall embankment
heights, thereby reducing the overall construction and material costs of the Flotation and BIOX TSF starter wall embankments. |
| · | The annual RoR is the highest during the first few years after deposition commences and decreases after
year four. |
| · | The Bilboes TSF can accommodate a maximum tailing cumulative volume of 21.7 Mt for the Flotation TSF compartment
and 1.6 Mt for the BIOX TSF compartment (Flotation and BIOX compartment) within the RoR limit below 2.5 m/year (at 1.35 t/m³). |
| · | The starter wall heights, for the Flotation and BIOX TSF compartments for the proposed deposition are
recommended as follows: |
‒ Flotation TSF compartment Phase 1 and Phase 2: |
|
1,153.5 mamsl. • |
‒ Flotation TSF compartment Phase 3: |
|
1,158.0 mamsl. |
‒ BIOX TSF compartment Phase 1: |
|
1,158 mamsl. |
| · | The phasing of the TSF is to be (Figure 18-3): |
| ‒ | The BIOX TSF constructed without being divided and therefore as a complete compartment, up to the Phase
3 wall elevation, while the Flotation compartment is to be divided into two compartments. |
| ‒ | A dividing / sacrificial wall be constructed to separate the Flotation TSF compartment into two compartments.
This wall is to be constructed from approved available mine waste (the same as for the original starter wall embankments). |
| ‒ | In addition to the dividing/ sacrificial wall a cut-off trench and protection berm are to be constructed
upstream of the sacrificial wall, in the Phase 2 Flotation compartment. |
| // | |
Figure 15-3: Phasing of Flotation
TSF Compartment – 240 ktpm
| · | The following phasing of the Flotation TSF compartment is suggested: |
| ‒ | Phase 1 – deposition volume of three years in the Phase 1 compartment up to the Phase 1 starter
wall elevation. |
| ‒ | Phase 2 – deposition volume up to the elevation of the sacrificial wall height with deposition taking
place in the Phase 2 compartment. The Phase 2 wall elevation will apply to the Phase 1 and Phase 2 TSF compartments. |
| ‒ | Phase 3 – deposition volume up to the elevation of the Phase 3 wall elevation with the Flotation
TSF compartment being operated as one deposition compartment, i.e. the Phase 1 compartment and Phase 2 compartment are merged and operated
as a single TSF. |
| ‒ | Phase 4 – the tailings elevation is above the Phase 3 wall height and the TSF is “selfbuilding”
with tailings, up to the final design elevation. |
| · | For the Flotation Phase 1 compartment, it is recommended that the temporary penstocks as well as the final
permanent penstock intake be constructed for operational use during Phase 1 deposition. Two additional temporary penstocks will be required
within the |
| · | Flotation Phase 2 compartment to allow decant water to drain sufficiently from the compartment. The final
permanent penstock will be utilized during the end of deposition on the Phase 1 compartment, as well as after the Phase 1 and 2 compartments
are merged into one (Phase 3 operation). |
| // | |
| · | Initially, the underdrainage system only needs to be constructed and operational for the Flotation Phase
1 compartment as well as for the entire BIOX TSF. Therefore, there will be an initial cost saving on the underdrainage system required
for the Flotation TSF. However, any tie-in systems or part thereof, that fall within the Phase 2 basin area will need to be constructed
during Phase 1, for ease and continuity of construction. |
| · | The solution trench, around the perimeter of the facilities is to be concrete lined, as it was agreed
that the “worst case” option in terms of tailings type and classification would be adopted as part of this assessment. |
| · | The siting of the Flotation and BIOX RWDs and silt traps are to remain as per the 2019 FS. |
| · | As the catchment area of Phase 1 is less than the overall TSF, only one of the Flotation RWDs needs to
be constructed as part of Phase 1, while the second will need to be constructed during Phase 2. The BIOX RWDs should be constructed during
Phase 1. |
| · | The outer containment walls for the Flotation and BIOX TSF compartments are to be constructed in stages
using approved available mine waste, developed in a downstream manner to fully contain all deposited tailings up to the point when the
tailings RoR is below 2.5 m/year. The waste rock material is assumed to have a friction angle of 1v:3h, slightly steeper than the conventional
industry guideline of 1v:4h, due to the material properties of the waste rock. |
| · | From previous geotechnical investigations, the soils in the area are about 0.4 m thick and generally sandy
clays grading to clayey sands. Field and laboratory permeability testing indicate permeability ranging from 10 - 5 m/s to 10 - 7 m/s and
on average 10 - 6 m/s. Maximum outflow rates in the clay layers should be 10 - 9 m/s for Class B facilities and 10 - 8 m/s for Class C
facilities. Thus, it is recommended that an investigation is undertaken to identify clay sources on or near the site for barrier construction.
Alternatively, GCL may be imported and used for the construction of the barrier system but will need to be costed. |
| · | The tailings sample is not considered representative of the tailings material as it was treated prior
to the geochemical analysis. The high leachable and total arsenic concentrations need to be verified by a repeat test. The treated tailings
also need to be verified that they will indeed classify as a Type 2 waste. |
| · | An options study should be undertaken on the Class C barrier system to identify other alternatives to
the typical Class C Landfill Barrier System. This may include extraction boreholes around the site, or a thick clay layer being placed
as a barrier system. |
| · | Therefore, it is recommended that the liner system previously recommended be implemented as part of this
IA. |
| · | The rates used for the CAPEX and OPEX were based on the best estimate rates available to SLR checked against
recent rates obtained by DRA and shared with SLR. However, SLR strongly recommends that the BoQ be issued to market as part of the next
Phase of design and the rates validated and benchmarked to ensure that the rates are in line with current costs. |
| · | At this level of design (Optimized IA) there are uncertainties that will only become clear as the next
project Phase commences, and design parameters are fixed and/or investigated further at more detailed design stages. |
| // | |
| · | For the current design an excessive amount of clay material is required for the Flotation and BIOX TSF
compartments as well as for the RWDs (Flotation and BIOX). Based on current information, the specified clay material is not readily available
on site or in the nearby vicinity and therefore will need to be sourced, leading to additional costs. Therefore, should the required volume
and type of clay material not be available, alternatives such as GCL may need to be imported at an additional cost. |
| · | Construction difficulties will arise due to the Phase 1 Flotation TSF being operational while the Phase
2 Flotation TSF is being constructed, (as with Phase 2 Flotation TSF being constructed while the Phase 3 Flotation is under construction).
This will be due to the operational facility being in direct proximity to a construction site. Further engineering design and consideration
needs to be implemented and incorporated in the next Phases of design. |
| · | Operational challenges will develop, including depositional constraints as well as correct pool management.
This holds true for all Phases of the TSF development. Additional penstocks have been included for the Phase 2 Flotation compartment to
aid with pool management. |
| · | The joining of already placed liner (Phase 1) to the new liner (Phase 2) will be challenging and will
need a good lining contractor to undertake the lining operation. |
| · | Exposed liner will become damaged by UV, rocks, and accidental and/or deliberate negligence. Additional
liner protection material as well as extra sandbags have been allowed for, but detailed design and construction CQA will be required. |
| // | |
| 16.1 | Historical Supply and Demand |
Gold is a precious metal refined and sold as bullion on the
international market. Aside from the gold holdings of central banks, current uses include jewellery, private investment, dentistry, medicine,
and technology (Figure 16.1).
Gold is mined in many countries around the globe; China, Australia
and Russia are major gold producers providing 31.5% of world gold supply with recycled gold being a significant part of global supply
(Figure 16.2). Globally jewellery is the main application sphere of this precious metal accounting for over 48% of total demand.
Figure 16-1: Historical Gold Supply
(2010 - 2023)
_______________________
§ Source:
World Gold Council
| // | |
Figure 16-2: Historical Gold Demand
(2010 - 2023)
About half of gold jewellery consumption is in India and China
and these markets’ trends greatly influence the overall gold industry. Investment in gold is another important application sphere
and its share is about 29%. Demand from national central banks has also been growing especially from banks of developing countries in
Latin America, the Middle East and Asia.
The supply and demand of gold does not follow typical supply
and demand logic as gold is indestructible and can easily be recycled and is stored in vaults of banks. Gold is therefore relatively liquid
and subject to the vagaries of global economics. These characteristics of the gold market make it challenging to forecast the gold price.
_______________________
| ** | Source: World Gold Council |
| // | |
Source: World Gold Council
Figure 16-3: Gold Price (2010 -
2023)
Over the past century, gold has consistently shown as both
a beacon of potential stability and a mirror reflecting global economic fluctuations. Gold's value over time is marked by significant
fluctuations influenced by economic policies, global crises, and shifts in demand.
With a backdrop of financial and geopolitical uncertainties,
the outlook for gold prices suggests a continued appeal of the precious metal as a so-called safe-haven asset. In recent years, gold has
demonstrated resilience in the face of global economic challenges, including inflationary pressures and currency fluctuations. Several
macroeconomic factors could shape the gold projections in the future:
| · | Inflation: While many assume a direct correlation between inflation and gold, the relationship is complex
and not as straightforward. Inflation can impact the metal, but other factors often mitigate its effects, |
| · | Currency Fluctuations: Gold and the US dollar share an inverse relationship. As the dollar weakens, gold
often rises, becoming more attractive to investors holding other currencies, |
| · | Geopolitical Tensions: Conflicts and political instability historically drive investors towards gold as
a so-called safe haven, potentially boosting its price during periods of heightened uncertainty. |
| · | Interest Rates: Gold's appeal can diminish with the expectation of rising interest rates, as higher yields
on bonds and savings accounts compete with the non-yielding metal. |
| 16.2 | Gold Sales in Zimbabwe |
The Gold Trade Act empowers the Minister responsible for Finance
to issue a Gold Dealers
License which entitles entities to export and sell gold from
Zimbabwe to customers of its choice. Prior to 1 June 2021, only FGR had the Gold Dealership License and therefore all gold bullion was
sold to FGR. With effect from 1 August 2021, all gold producers can directly sell any incremental production to customers of their choice
using FGR’s license to export. Caledonia’s Blanket Mine is currently selling 75% of its gold to a customer of its choice outside
Zimbabwe by exporting the gold using FGR’s license. Sales proceeds from the exported gold are received directly into Blanket's bank
account in Zimbabwe. As all Bilboes production is considered incremental, Bilboes will be able to choose to sell its gold directly to
customers of its choice or to continue selling to FGR.
| // | |
Bilboes is confident that it will be able to export and sell
its gold production on similar terms as those currently in place between FGR and Blanket.
The Blanket toll arrangement which will be similar to Bilboes
is outlined below:
| · | Lodgments to FGR can be made on any day of the week. |
| · | Melting and assaying charges of US$ 21/kg gross bullion weight applies. |
| · | The applicable Government royalty of 5% is deducted from proceeds due to the customer. FGR collects half
of the 5% royalty which is payable to the Government of Zimbabwe in physical gold. |
| · | 25% of the Blanket gold ounces is sold to FGR and settled in ZIG. Pricing is based on the previous day’s
LBMA PM fix of the day of packing for export. |
| · | The ZiG portion is settled within 7 days. |
| · | 75% per cent of the gold ounces are refined at FGR and exported by Caledonia using Fidelity’s gold
dealing license to a refiner outside Zimbabwe which undertakes further refining. |
| · | The refiner outside Zimbabwe pays 90% of the value on the day of lodgement and 10% after further refining.
Pricing is based on the LBMA AM fix price on date of lodgement. |
| · | FGR charges a 1.24% toll refining fee of the gross value of the export proceeds. |
| // | |
| 16.3 | FGR Gold Price Predictions |
A summary of the predicted gold prices for 2024 are presented
in Table 16.1.
Table 16.1: Predicted Gold Price
Analyst/Firm |
2024 Gold Price Prediction |
Bank of America |
US$ 2,400/oz by end of 2024 |
UBS Bank |
US$ 2,200/oz by end of 2024 |
Goldman Sachs |
US$ 2,133/oz by end of 2024 |
World Bank |
US$ 1,900/oz by end of 2024 |
Citibank |
US$ 2,400/oz by end of 2024 |
ING |
US$ 2,100/oz by end of 2024 |
Wells Fargo |
US$ 2,100 – 2,200/oz by end of 2024 |
Ronald Stoeferle, Incrementum AG |
US$ 2,500/oz by end of 2024 |
Zach Scheidt, Rich Retirement Letter |
US$ 3,000/oz by end of 2024 |
_______________________
‡‡ 2024 Gold Price Prediction, Trends,
& 5-Year Forecast (goldsilver.com)
| // | |
| 17 | ENVIRONMENTAL STUDIES, PERMITTING, AND PLANS, NEGOTIATIONS, OR AGREEMENTS WITH LOCAL INDIVIDUALS OR GROUPS |
The natural environment within the project site has been significantly
transformed by existing mining operations. The surrounding environment is more natural with disturbances from communities and subsistence
farming activities. Other mining operations do occur in the region, however over time several mines in the area have been closed. The
EIA (SLR, 2019) identified a number of potential environmental impacts as shown in Table 17.1.
Table 17.1: Potential Environmental
Impacts
Potential Environmental Impacts |
Mitigation |
Significance After Mitigation |
Potential loss of soil and related grazing land capability within the proposed project footprint |
Soil can be conserved and reused during rehabilitation |
Low |
Potential contamination of soils, surface water and/or groundwater features |
Design of potentially contaminating facilities and managing the storage and handling of polluting substances and related clean-up of spills reduces the Intensity of these potential impacts |
Medium to High |
Alternation of drainage patterns and related downstream functionality of aquatic habitat due to encroachment of the Bubi open pit into the nonperennial Bubi River |
The Bubi River can be diverted to ensure that that the Hydraulic connectivity of the river is retained, and pollution, sedimentation and erosion impacts are generally avoided. |
Medium |
Potential contamination of surface and groundwater resources from various
operational activities and contamination from the new TSF and
WRDs |
Implementation of industry-aligned surface water management measures and a composite lining for the floatation compartment and full HDPE liner for the BIOX® compartment of TSF |
Surface water = Medium
Groundwater = High |
Lowering of groundwater levels potentially affecting third party water supply should third party boreholes be located within the dewatering cone of depression |
Any third-party water sources that have a proven decrease in yield or dry up because of the proposed operations would be compensated with an alternative water supply of equivalent quality and quantity |
Medium |
Potential reduction in ambient air quality due to particulate emissions |
Implementation of an air quality and dust management plan during the implementation and operation of the proposed project lowers the intensity, and probability of such impacts occurring |
Medium (operational Phase) to Very Low (construction and decommissioning
Phases) |
Elevation in ambient noise levels creating a potential disturbance to nearby receptors. |
Incorporating mitigation into the site design, as well as adopting sound management practices (e.g., maintaining machinery and equipment in good working order). |
Medium (operational
Phase) to Low
(construction and decommissioning
Phases) |
| // | |
Potential Environmental Impacts |
Mitigation |
Significance After Mitigation |
Visual disturbance to nearby local communities |
Undertaking rehabilitation throughout the course of the proposed operations, |
Low |
Physical destruction and general disturbance of terrestrial and/or
aquatic biodiversity |
By ensuring that the project footprint for planned clearing and infrastructure establishment is clearly demarcated and all areas of increased ecological sensitivity, outside of the mining footprint are designated |
Medium |
Potential Environmental Impacts |
Mitigation |
Significance After Mitigation |
|
as No-Go areas would limit the associated significance of these impacts |
|
The EIA (SLR, 2019) concluded that the proposed project presents
several potential positive and negative impacts associated with the unmitigated scenario. With mitigation (in the residual impact scenario)
some of the identified potential impacts can be prevented and the remainder can be managed and mitigated to remain within acceptable environmental
limits so long as the mitigation set out in the ESMP is implemented and Bilboes develops, implements, and annually reviews the ESSMS.
Positive impacts can be enhanced by developing and implementing a Community Development Plan as set out in the ESMP.
Bilboes is committed to implementing the mitigation measures
within the ESMP together with the ESSMS which will be implemented as part of Bilboes on-going efforts of continuous environmental improvement.
The management system will contain plans and procedures to help manage environmental aspects and impacts and help ensure legal compliance.
| 17.2 | Waste, Tailings, Monitoring and Water Management |
| 17.2.1 | Tailings Management and Disposal |
Gold recovery at Bilboes would entail a two-stage process that
would result in the generation of two different tailings streams - Flotation and BIOX® tailings. The TSF would be developed with two
separate compartments to accommodate each tailings stream.
The proposed liner system for each comportment would incorporate
(from top down):
| · | Floatation Compartment – A 1.5 mm HDPE geomembrane, a base layer of 300 mm selected clayey material
(compacted in 2 x 150 mm thick layers), |
| · | BIOX® Compartment – A 2 mm HDPE geomembrane, a base layer of 600 mm selected compacted clay
liner (compacted in 4 x 150 mm thick layers), |
| · | Both compartments would have a ripped and re-compacted 150 mm in-situ base layer, |
| · | The TSF would incorporate a filter drainage system comprising an 8.5 m wide, 500 mm deep toe drain located
immediately adjacent to the upstream toe of the starter wall for the Floatation compartment and a 7.5 m wide, 500 mm deep toe drain located
immediately adjacent to the upstream toe of the starter wall for the BIOX® compartment, |
| // | |
Both compartments would have a reticulation of above-liner
finger drains consisting of a configuration of 160 mm and 110 mm diameter slotted seepage collector pipes in the basin discharging
to the solution trench independently of the toe drains to allow monitoring. The proposed decant systems consist of temporary intake structures
(designated FT) and permanent intakes (designated FP). The intake structures have both top and side inlets.
There would be on-going rehabilitation of tailings through
the application of the rising green wall. The TSF design slopes adopted (1V:4H) are considered environmentally stable to allow for indigenous
vegetation growth with minimal ongoing maintenance. To assist with the vegetation establishment, the vegetation will be manually planted
and irrigated during the initial stages. A cover involving topsoil and subsoil (in combination with the rocky waste rock material placed
during construction protruding) will be progressively placed onto the side slopes of the TSF as the same is developed. These protrusions
are advantageous as they mimic natural slopes and dissipate the kinetic energy of rain drops as they strike the surface.
The tops surface will be covered with topsoil mixed into tailings.
The top surface will then be paddocked into smaller catchments to reduce water flow lengths.
The Bilboes TSF is classified as a Medium Hazard to High Hazard
facility due to the number of residents in zone of influence estimated to be between 8 and 16 (determined in accordance with terms of
the South African Code of Practice for Mine Residue Deposits (SABS 0286:1998) and the requirements of Mineral Regulation 527 of 23 April
2004). The classification considered the two compartments as one facility.
| 17.2.2 | Waste Rock Management and Disposal |
The planned WRD construction method would entail the following:
| · | A nominal wall of waste material would initially be constructed to confine the extent of the dumping area
within the planned WRD footprint. |
| · | Waste material will be delivered to WRD by truck and tipped from the leading edge of the WRD towards the
inside of the WRD footprint. The waste will then be spread and shaped as necessary by earthmoving equipment. |
| · | The WRD would then be developed in successive lifts of up to 10 m in height, with each lift being completed
before commencement of the subsequent lift. |
The WRD will be constructed at an angle of repose slopes of
approximately 35°.
In principle, the WRD lift heights shall be limited to 10 m
with a minimum of a 10 m berm, with an overall height of 40 m. Seepage from the toe of the WRD, as well as runoff from the slopes, would
be controlled by the construction of an outer containment wall. The containment wall will be the boundary between the clean and potentially
contaminated water systems for the purposes of stormwater management.
Some compaction of the waste is expected to take place during
placement as trucks pass repeatedly over previously placed material on their way to and from the advancing faces of the WRDs. While compaction
of wastes is desirable to maximize density and storage capacity, it is not a requirement for structural stability. Compaction will assist
in reducing differential settlements with time, which will assist in ensuring the longer-term integrity of surface water management measures.
| // | |
| 17.2.3 | Non-Mineralized Waste Management |
Non-mineralized waste (including general industrial waste,
medical clinic waste, hazardous industrial and domestic waste) would be temporarily handled and stored on site before being removed for
recycling by suppliers, reuse by scrap dealers or final disposal at the existing waste disposal area located at Isabella. Bilboes has
a designated burning site for all waste materials associated with cyanide packaging and hazardous waste on the heap leach pad where all
leachate goes into the heap leach cyanide circuit as recommended by the cyanide suppliers. An internal waste management procedure will
be developed for waste generated by the project.
With respect to sewage, it is proposed that the existing sewage
treatment facility located at Isabella would handle the sewage generated. It is proposed that a sewage treatment plant would be established
at Bubi.
| 17.2.4 | Site Environmental Monitoring |
The proposed monitoring programme is detailed in the ESMP for
the proposed project. The aspects for which monitoring is proposed includes:
| · | Annual monitoring (physical observation) for erosion, as well as slope / TSF failure, |
| · | Monthly surface and groundwater monitoring (of parameters including water quality, volumes, levels, spillages,
and management infrastructure), |
| · | Monthly updating of the site-wide water balance (including biennial updates of the water balance model), |
| · | Air and noise monitoring to establish baseline constituent concentrations / ambient noise levels, as well
as regular monitoring during construction and operations, as applicable. |
Requirements for post-closure monitoring to determine whether
the mitigation and rehabilitation measures are effective would be incorporated into a final Closure Plan to be compiled for the operations
prior to the commencement of decommissioning. Water Management
There is evidence that the Bembezi, Mdutshane and Bubi Rivers
have been impacted upon by various anthropogenic activities in the broader area. Furthermore, the planned widening of the open pits at
Bubi would encroach directly on the Bubi River and the tributary located within Bubi claims area. This would have a material impact on
this feature and may have an impact on downstream water users. It is thus recommended that the Bubi River be diverted around the proposed
expansion of the southern open pit to ensure that the hydraulic connectivity of the river is retained, and that pollution, sedimentation
and erosion impacts are avoided.
The following measures could be implemented to allow improved
water management and limit the risk of flooding the southern open pit during a high flow event in the Bubi River.
The measures to be implemented by Bilboes to address potential
adverse water quality effects and to ensure that the planned infrastructure is constructed, operated, and maintained to comply with the
provisions of the IFC guidelines, include:
| · | Separating clean water systems from dirty water systems, Minimizing the size of dirty areas and divert
clean run-off and rainfall water around dirty areas and back into its normal flow in the environment, |
| // | |
| · | Locating all activities and infrastructure outside of the specified zones and/or flood lines of watercourses,
as far as possible. Where this is not possible, the affected area should be remediated/rehabilitated to restore the original ecological
function post-closure, |
| · | Maintaining specified zones around surface water features in instances where flood lines are unknown or
un-surveyed, |
| · | Incorporating suitable erosion protection measures at all discharge points, should any discharge be required.
Furthermore, all discharges from the mine into the environment will comply with the IFC Effluent discharge standards. |
An approved EIA is required in terms of the Environmental Management
Act (Chapter 20:27) No. 13 of 2002 and the Mines and Minerals Act (Chapter 21:05) of 1996. The ESIA was undertaken for the project to
satisfy the requirement and an ESIA Report was completed for submission to EMA within the first quarter of 2020. Thereafter, SLR held
a public feedback meeting to disclose the findings of the ESIA Report to the identified stakeholders. A record of this disclosure process
was compiled and submitted to EMA. An EIA certificate was issued to Bilboes for the project in February 2021 and was and was valid for
two years to February 2023. The EIA certificate is renewable on an annual basis subject to conditions which include project update reports,
compliance to Environmental Management Plans (EMP) outlined in the ESIA Report and notification to EMA for any changes in the project
likely to alter the project as stipulated in the ESIA Report. The current EIA certificate is valid until March 2025 and the renewal process
will continue annually for the duration of the operations.
Other project related licenses/permits currently in use include
explosives (purchase and storage), firearms, medicines control, public health (medical examination), water abstract and hazardous substances
(importation, transportation, storage and use), solid waste disposal which are renewed quarterly or annually when become due. The conditions
of renewal are limited to payment of applicable fees to the relevant statutory bodies. A total of US$ 70,000 is required to cover all
the license fees and permits on an annual basis.
| 17.4 | Social and Community Related Requirements and Plans |
An ESMP has been developed which contains the environmental,
social and safety management and monitoring commitments that Bilboes will implement to manage the negative impacts and enhance the positive
impacts identified in the EIA.
To mitigate against the loss of, or reduced access to, land
for livelihood activities, a LRP will be compiled and implemented prior to the commencement of construction.
As part of the existing operations Bilboes have undertaken
several CSR programmes. These include the supply of various community boreholes at communities and local schools, building and repairs
of school blocks, the repair of various local roads, excavation and scooping of dams and provision of various other services including
access to health facilities at the mines and transport in cases of emergency.
To address potential issues related to employment, Bilboes
will develop a fair and transparent labor, working conditions and recruitment policy. The policy will comply with local law, IFC Performance
Standard 2: Labor and Working Conditions, and International Labor Organization (ILO) conventions.
| // | |
To optimize local small business development, a local procurement
policy will be developed and implemented and communicated to all local stakeholders.
The Stakeholder Engagement Plan developed for the project will
be maintained and updated to provide a formal procedure for communications with the regulatory authorities and communities.
| 17.5 | Social / Community Issues |
Based on the EIA undertaken for the proposed project, social
or community impacts that were identified and assessed include the following:
| · | Positive economic impact because of the direct construction and operational project expenditure, direct
and indirect business opportunities. Significance after mitigation - Very High Positive, |
| · | Potential reduction of access to land for livelihood activities (e.g., cattle ranching and subsistence
agriculture) undertaken within the mine claims area. A key recommendation to ensure that these land users are appropriately identified,
engaged, and compensated. Significance after mitigation - Medium, |
| · | Inward migration due to the expectation of employment. Bilboes should aim to source most employees from
the surrounding local communities, as far as possible. Significance after mitigation - High to Medium, |
| · | Various health and safety risks for third parties are associated with the proposed project. While the
likelihood of incidents is deemed to be low (with mitigation) any injuries or fatalities of third parties would be of high intensity.
Significance after mitigation - Medium, |
| · | No cultural-heritage resources were found to be located within the proposed project footprint. Significance
after mitigation - Very Low. |
A conceptual closure plan and LoM closure liability estimate,
based on the environmental, social, and economic risks identified in the EIA, is included in the EIA. Furthermore, the closure issues
and concerns raised by stakeholders were also incorporated, where applicable.
Generally accepted “good international practice”
mine closure methods were used as the basis for the conceptual closure plan, as well as, for determining the unit rates for the various
closure components used in the LoM liability calculation. The mine closure methods also conform to the statutory requirements of Zimbabwe
EMA who are the regulatory body.
Mine closure planning is a dynamic process that is integrated
with LoM planning to ensure a seamless transition from the operational to the decommissioning Phases in the mine life cycle. The environmental
objective for closure is to minimize the impacts associated with the decommissioning and closure of the mine and to achieve post closure
land use as outlined.
The conceptual closure plan objectives include the following:
| · | Environmental damage is minimized to the extent that it is acceptable to all parties involved. |
| · | The land is rehabilitated to achieve a condition approximating its natural state (as far as practicable),
or so that the envisaged post closure land use/land capability is achieved. |
| // | |
| · | Some of the smaller open pits shall be completely backfilled with material from the overburden/WRDs. Inert
building rubble from the decommissioning activities can also be buried in the pit voids. The remaining open pits would not be backfilled
and remain open. The pit sidewalls and end-walls will only be ‘made safe. |
| · | All surface infrastructure, excluding the TSF and any other surface infrastructure that will support the
envisaged post-closure end use, will be removed from site after rehabilitation. |
| · | Contamination beyond the mine site by wind, surface run-off or groundwater movement will be prevented
through appropriate erosion resistant covers, containment facilities (i.e., stormwater ponds) and drainage controls. |
| · | Mine closure is achieved efficiently, cost effectively and in compliance with the law. |
| · | The social and economic impacts resulting from mine closure are managed in such a way that negative socio-economic
impacts are minimized. |
| · | Based on the above, the closure outcomes for the mine site are assumed to be as follows: |
| · | To achieve chemical, physical, and biological stability for an indefinite, extended time period over all
disturbed landscapes and residual mining infrastructure |
| · | To protect surrounding surface water, groundwater, soils, and other natural resources from loss of utility
value or environmental functioning |
| · | To limit the rate of emissions to the atmosphere of particulate matter and salts to the extent that degradation
of the surrounding properties’ land value and land capability does not occur. |
| · | To create a final land use that has economic, environmental, and social benefits for future generations
that outweigh the long-term aftercare costs associated with the facility. |
| · | These broad closure objectives and outcomes will be continually refined as operations continue. |
| 17.7 | Estimated Environmental Costs for Closure |
The quantities used in the closure liability calculations were
derived from the layout plans and general arrangements for the project; the project infrastructure details within the feasibility study
report; and the proposed mining and deposition schedule. The closure liability calculation has been determined for the LoM (end of year
10) and is calculated to be US$ 32 m (excl. VAT) (2023). The closure liability calculations will be regularly reviewed and updated during
the project up and until the commencement of closure activities (i.e., final closure plan). Ongoing environmental rehabilitation is based
on a unit rate of US$ 0.25 / t plant feed.
The QP is of the opinion that the current plans to address
issues related to environmental compliance, permitting and local individuals and groups are adequate.
| // | |
| 18 | CAPITAL AND OPERATING COSTS |
A Class 4 estimate (AACE 4) has been undertaken which has an
accuracy range of cost plus +20% to 50% on the high side and cost minus -15%-30% on the low side.
| 18.1 | Capital Cost Estimate |
| 18.1.1 | Basis of Estimate - Mechanical |
The method used to determine the Capital Cost Estimate (CCE)
for the IA Production Trade Off Study consisted of the following steps:
| · | Step 1: The estimate was based on the original development of the 2019 Bilboes Project FS, which was revalidated
in 2021 and 2023 and updated by submissions from other consultants (i.e. BIOX plant costed by Metso, and Tailings Storage Facility costed
by SLR Consultants). |
| · | Wherever information was not revalidated, DRA database information was utilized, escalated to the new
project base date, or factorized. |
| · | The following costing areas were identified as optimization areas: |
| ‒ | Updated TSF costs by SLR, |
| ‒ | Buildings (updated with client estimate received), |
| ‒ | Chinese sourced material for steelwork and platework, |
| ‒ | Major mechanical equipment sourced from China (crushers, mills, flotation cells, thickeners for example). |
| · | Step 2: Factors were carefully developed from the established Phase 1 and 2 “known costs”
based on Work Breakdown Structure (WBS) and discipline level breakdown. Factors were either developed from the mechanical supply costs,
direct field costs, or relevant discipline supply costs. |
| · | Step 3: For equipment, revalidated mechanical supply costs were utilized. |
| · | The factors developed in Step 2 were then applied to all disciplines and factored either from the newly
established mechanical supply costs, direct field costs or discipline supply costs. |
| · | Wherever detailed costs were calculated for the applicable discipline (i.e. mining costs), detailed costs
superseded the factoring method and phase. |
| 18.1.2 | Basis of Estimate – Civils and Earthworks |
| · | All quantities and costs were revalidated for 2023, |
| · | A revised Geotechnical Report was not completed at this stage of the project, |
| · | The bulk of earthworks quantities were modelled in three dimensions, ➢
Allowances were made for engineered mattresses for lightly loaded buildings. |
| · | Piling was allowed for dynamically and heavily loaded structures. |
| // | |
| · | Concrete quantities were generated by using the DRA database for similar structures, |
| · | Reinforcement allowed at 80 kg to 120 kg depending on the structure type. |
| · | Rates in US$ were allowed for and based on rates for works recently executed in Zimbabwe. |
| · | Preliminary and General (P&G's) costs for earthworks were allowed for a percentage (%) of measured
work and were based on latest P&G percentages for works recently executed in Zimbabwe. |
| 18.1.3 | Basis of Estimates – Mechanical Equipment |
| · | The original 2019 CCE mechanical equipment structure in the CCE was used as the basis for revalidation
and is in accordance with the Mechanical Equipment List (MEL), |
| · | The 2019 selected vendor quotations were used and sent back to the vendors for revalidation, |
| · | Some 97% of the mechanical costs were revalidated by vendors, |
| · | If no response was received from a vendor or the vendor did not quote for a specific item, the Estimating
department reverted to using a database price, escalation from 2021 to current base date or factoring, |
| · | The CCE used around 1% of costs from the DRA database costs, escalation amounted to 2% and 0% factorisation, |
| · | For 2023, Metso validated costs for the BIOX area, |
| · | Mechanical installation rates were revalidated by a SMP contractor, |
| · | Most of the information in the CCE remained unchanged, with exception to the follow mechanical equipment
pricing, which was updated with equipment sourced from China: |
| 18.1.4 | Basis of Estimates – Steelwork, Platework and Piping |
| · | The original 2019 Bill of Quantity (BOQ’s) were sent to the selected SMP contractors for revalidation
and rates included in the CCE, |
| · | The BIOX plant supply was provided by the vendor, Metso. |
| · | P&G's were quoted by a SMP contractor and allowed for as a percentage of measured work on the supply
and installation costs, |
| · | A SMP contractor quoted for transportation of supplied material, |
| · | Piping was factored from mechanical supply costs. |
| // | |
| 18.1.5 | Basis of Estimates – Electrical Control and Instrumentation |
| · | The MEL was used as bases of design, |
| · | Estimated lengths were used to determine cable and cable support quantities, |
| · | Lighting and small power quantities were estimated using the process plant footprint, |
| · | Lightning protection and earthing requirements were estimated according to plant buildings, |
| · | Instrumentation quantities based on process requirements, |
| · | The control system based on process requirements and instrumentation quantities. |
| · | Bulk power cost received from ZETDC, |
| · | Major electrical equipment costs were based on quotations received for current execution projects, |
| · | Control and instrumentation equipment costs were based on recent quotations, |
| · | Installation costs were based on budget tender rates received for other Zimbabwean projects, |
| · | P&G's were calculated as a percentage of supply and installation costs on recently completed in-country
projects. |
| // | |
| 18.1.6 | Capital Costs Summary |
The mining cost for mining are combination of site establishment
and pre-development during the production ramp up which consists of the first 9 months of production (Table 18.1).
Table 18.1: Capital costs Summary by
Discipline
Description |
(US$ m) |
Open Pit Mining |
25.54 |
Tailings Storage Facility |
75.25 |
Earthworks |
36.81 |
Civils and Infrastructure |
14.48 |
Buildings |
5.85 |
Steelwork |
16.34 |
Conveyor Steelwork |
4.37 |
Platework |
12.49 |
Conveyor Platework |
0.38 |
Mechanicals |
76.11 |
Conveyor Mechanicals |
1.90 |
Vendor Commissioning |
4.00 |
Piping and Valves |
19.19 |
EC&I |
35.36 |
Consumables |
2.25 |
Spares |
7.05 |
Description |
(US$ m) |
Construction Services |
0.54 |
Project Services |
22.36 |
Owners Cost |
8.88 |
Estimate Allowance |
33.82 |
Total |
402.97 |
| 18.2 | Operating Cost Estimate |
The operating cost estimate has been completed from a zero
base and presented in US$.
Costs associated with labor, materials and consumables have
been included in this estimate.
| // | |
| 18.2.1 | Mining Contractor Costing |
The average mining cost based two mining contractor submissions
received is US$ 2.65/t including the plant feed transport cost from all mining areas process plant. The cost breakdown is shown in Table
18.2. A diesel price of US$1.52 was used in all cost modelling.
Table 18.2: Life of Mine Mining Contractor
Operating Cost Summary
Total LoM Cost Summary |
Base Case Cost 240 – 180 ktpm (US$ m) |
Base Case Cost 240 – 180 ktpm (US$/t) |
Time Related P&G |
65.8 |
0.29 |
Load-Haul-Dump Cost |
421.9 |
1.88 |
Total Drilling Cost |
72.9 |
0.32 |
Total Blasting Cost |
28.2 |
0.13 |
Plant feed Re-handle at ROM Tip |
4.9 |
0.02 |
Services and Rehabilitation Cost (Allowance) |
2.4 |
0.01 |
Total Bilboes Mining Cost |
596.1 |
2.65 |
| 18.2.2 | Process Plant Operating Cost |
The concept level operating cost estimate was completed from
a zero base. All labor, energy costs, materials and consumables have been included in this estimate. The bulk of the inputs were generated
by DRA based on outcomes from mass balance, equipment sizing and budget quotations for the supply of reagents from typical suppliers within
the region. Labor rates were supplied by the Bilboes owners’ team with the compliment developed to support the plant operation.
Engineering maintenance costs are based on a % applied to direct costs and can be treated as an annual allowance.
The Operating Expenditure (OPEX) cost for the process plant
for each Phase and scenario is provided in the tables below as well as the reagent cost and consumption for Isabella McCay’s and
Bubi ore.
| 18.2.2.1 | Reagent Consumption and Supply Rates |
Table 21-3 presented below provides a summary of the expected
reagent and consumable consumptions for Isabella McCay’s and Bubi ore, based on results obtained from test work, vendor specifications,
benchmark data and mass balances.
| // | |
Table 18.3: Reagent Cost and Consumption
for Isabella McCay’s and Bubi
Description |
Consumption Rate, kg/t ore |
Supply Cost, US$/t RoM |
Supplier Name |
Isabella McKay’s |
|
|
|
Collector (SEX) |
0.150 |
3,125 |
BetaChem (SA) |
Modifier (CuSO4) |
0.100 |
3,170 |
BetaChem (SA) |
Frother (DOW) |
0.045 |
3,063 |
BetaChem (SA) |
Depressant (Na2SO3) |
0.350 |
500 |
BetaChem (SA) |
Depressant (Starch) |
0.110 |
1,825 |
BetaChem (SA) |
Sulfuric acid (H2SO4) |
1.050 |
575 |
Curechem (Local) |
Limestone |
2.183 |
65 |
PPC Zim |
Description |
Consumption Rate, kg/t ore |
Supply Cost, US$/t RoM |
Supplier Name |
Lime |
3.074 |
330 |
PPC Zim |
Nutrient |
0.430 |
423 |
- |
Anti-scalant |
0.002 |
3,810 |
- |
Corrosion inhibitor |
0.002 |
3,542 |
- |
Biocide |
0.002 |
4,500 |
- |
Defoamer - BIOX |
0.001 |
5,940 |
- |
Defoamer - CIL |
0.005 |
5,940 |
- |
Flocculant |
0.017 |
4,000 |
- |
Cyanide |
1.000 |
3,030 |
Curechem (Local) |
Carbon |
0.001 |
3,540 |
Acol chemicals (Local) |
Hydrochloric acid |
0.025 |
770 |
Curechem (Local) |
Caustic soda (NaOH) |
0.065 |
1,050 |
Curechem (Local) |
SMBS |
0.250 |
860 |
Acol chemicals (Local) |
Copper sulfate (CuSO4) |
0.005 |
3,167 |
Acol chemicals (Local) |
Bubi |
|
|
|
Collector (SEX) |
0.150 |
3,125 |
BetaChem (SA) |
Modifier (CuSO4) |
0.100 |
3,170 |
BetaChem (SA) |
Frother (DOW) |
0.045 |
3.063 |
BetaChem (SA) |
Depressant (Na2SO3) |
0.350 |
500 |
BetaChem (SA) |
| // | |
Depressant (Starch) |
0.110 |
1,825 |
BetaChem (SA) |
Limestone |
45.708 |
65 |
PPC Zim |
Lime |
7.831 |
330 |
PPC Zim |
Nutrient |
0.860 |
423 |
- |
Anti-scalant |
0.003 |
3,810 |
- |
Corrosion inhibitor |
0.003 |
3,542 |
- |
Biocide |
0.003 |
5,727 |
- |
Defoamer - BIOX |
0.001 |
5,940 |
- |
Defoamer - CIL |
0.020 |
5,940 |
- |
Flocculant |
0.030 |
4,000 |
- |
Cyanide |
2.000 |
3,030 |
Curechem (Local) |
Carbon |
0.012 |
3,540 |
Acol chemicals (Local) |
Hydrochloric acid |
0.050 |
770 |
Curechem (Local) |
Caustic soda (NaOH) |
0.130 |
1,050 |
Curechem (Local) |
SMBS |
0.500 |
860 |
Acol chemicals (Local) |
Copper sulfate (CuSO4) |
0.1 |
3,167 |
Acol chemicals (Local) |
The estimated average running load has been calculated using
expected power draw from the equipment. Plant power has been based on grid supply at a unit rate of 0.10 US$/kWh. A summary is shown in
Table 18.4.
Table 18.4: Process Plant OPEX –
Power
Description |
Unit |
Value |
Source |
Power Supply Cost |
US$/kWh |
0.10 |
Bilboes Owners Team |
Power Draw: Isabella McCay’s |
kWh/t RoM |
66 |
Calculated |
Power Draw: Bubi |
kWh/t RoM |
114 |
Calculated |
An annual maintenance allowance has been included and is based
on a percentage of mechanical equipment, platework, steelwork, ECI, piping and valve capital costs. An allowance equivalent to 5% has
been included in the cost estimate.
Labor rates have been supplied by the Bilboes owners’
team. The compliment has been reviewed between DRA, Bilboes and Metso Outotec covering the main process plant and BIOX for each scenario.
| // | |
Costs associated with the laboratory covering labor, consumables,
and sample analysis have been considered. An estimated cost of 0.177 US$/t RoM was used for the various scenarios.
| 18.2.2.6 | Tailings Storage Facility Deposition and Operation |
SLR have conducted a concept level revalidation costing exercise
for the tailing storage facility covering both the flotation and BIOX tailings storage. A unit operational cost of US$ 0.30/t flotation
tails and US$ 0.49/t BIOX tails has been estimated and used in the cost estimate.
| 18.2.2.7 | Operating Cost Estimate Summary |
Table 18.5 provides an approximate breakdown of operating costs
per major section of the proposed Bilboes plant for each scenario and Phase of the project.
Table 18.5: Process Plant OPEX
Description |
Unit |
Phase 1: 240 ktpm IM |
Phase 2: 180 ktpm Bubi |
Variable |
US$ m/a |
37.93 |
53.33 |
Reagents and Consumables |
US$ m/a |
20.58 |
34.51 |
Power |
US$ m/a |
9.64 |
10.09 |
Maintenance |
US$ m/a |
7.70 |
8.73 |
Fixed |
US$ m/a |
12.31 |
17.17 |
Power |
US$ m/a |
9.23 |
14.45 |
Labor |
US$ m/a |
1.75 |
1.75 |
Tailings deposition |
US$ m/a |
0.82 |
0.58 |
Laboratory |
US$ m/a |
0.51 |
0.38 |
Overview |
|
- |
- |
RoM |
t/a |
2.88 |
2.16 |
Total variable |
US$ m/a |
37.93 |
53.33 |
Total fixed |
US$ m/a |
12.31 |
17.17 |
Total |
US$ m/a |
50.24 |
70.49 |
Unit cost |
US$/t ore |
17.44 |
32.64 |
| 18.2.3 | General and Administration Costs |
The G&A cost includes administrative personnel, general
office supplies, safety and training, travel (both on site and off site), independent contractors, insurance, permits, fuel levies, security,
camp power, camp costs, ICT, relocation, and recruitment.
The costs mentioned above are not directly chargeable to the
mining and process areas and hence are grouped together in general and administrative costs. Total G&A costs amount per scenario Phase
is shown in Table 18.6.
| // | |
Table 18.6: General and Administrative
Cost
Plant Throughput (ktpm) |
G&A Cost (US$ m/a) |
IM 240 ktpm |
4.91 |
Bubi 180 ktpm |
4.91 |
| // | |
The potential economic viability and performance of the IA
has been determined through developing a financial model founded on the results derived from the study and information provided by the
Bilboes owner's team only using indicated and measured resources. The results tabled in this section have been based on forward looking
statements, including (but not limited to) the feed profiles, grade profiles, gold recoveries, capital and operating cost requirements
and gold pricing profiles. As such, the results presented in this section should be treated with caution and are meant for decision-making
purposes only.
Readers are cautioned that Mineral Resources are not Mineral
Reserves and have no demonstrated economic viability.
The economic analysis for this option has been carried out
using Discounted Cash Flow (DCF) methodologies. The analysis has been based on earnings after taxation modelled in constant terms and
does not consider the effects of inflation, interest, escalation, and other financial charges. The economic model has been populated on
a 100% equity basis and does not consider alternative financing scenarios. Financing related costs such as interest expense, withholding
taxes on dividends and interest income, are excluded from the economic model. Additional exclusions pertaining to capital and operating
costs can be sourced from the relevant report chapter detailing these sections.
The interpretation of the taxation and the associated legislation
relevant to Zimbabwe has been based on information available in the public domain as well as guidance received from the Bilboes team.
DRA does not provide expert advice on taxation matters. VAT refunds and exemptions have not been considered in the economic model. Any
other tax or levy, not explicitly defined, has not been considered in the model. The tax model used should be regarded as conceptual but
is deemed to be suitable for this level of study. It is recommended, during the next project phase, to seek validation through a third-party
consulting firm who specialize in taxation and legislative conformance in Zimbabwe.
Cash flows considered in the cash flow model include annual
revenue, operating costs, initial capital expenditure, Stay in Business (SIB) capital allowance, capital contingency, environmental rehabilitation
capital allowance, royalties (to government and Baker Steel) and income tax presented on a year-by-year basis. The project start date
has been based on year 2026. All currency figures are reported in US$ with all cashflows presented in financial years starting in January
and ending in December.
| 19.3 | Sources of Information |
The basis of the financial evaluation has been founded on information
sources from DRA and the Bilboes owners’ team. An overview of key sources of information is presented in Table 19.1.
| // | |
Table 19.1: Economic Analysis - Sources
of information
Description |
Source of information / Responsible/ Notes |
General |
|
Discount rate |
Bilboes Owners Team |
Royalty tax rate |
Bilboes Owners Team |
Aids levy |
Bilboes Owners Team |
Macro Variables
Exchange rates |
Bilboes Owners Team |
Product pricing |
Bilboes Owners Team |
Production Schedules |
|
RoM tonnes and ounces |
DRA |
Initial Capital Expenditure (CAPEX)
Mining |
DRA |
Process plant |
DRA (with input from others) |
TSF |
SLR |
Stay in Business (SIB) Capital
Mining |
DRA |
Process plant |
DRA |
Operational Expenditure (OPEX)
Mining |
DRA |
Process plant |
DRA (with input from others) |
TSF |
SLR |
G&A |
Bilboes Owners Team |
Revenue
Product recoveries |
Bilboes Owners Team (previous testwork) |
Product pricing |
Bilboes Owners Team |
| // | |
| 19.4 | Contractual Agreements |
No significant contractual agreements have been concluded.
The following agreements are considered as the basis
for the economic analysis:-
| · | The basis of the mining cost estimate was that all mining will be done by an experienced mining contractor. |
| · | The EPCM Contractor will manage and co-ordinate the activities of the appointed construction contractors. |
| · | These appointed construction contractors will perform the construction operations for the duration of
the construction phase. |
| · | Bilboes will enter into a BIOX® Technology License Agreement with Outotec for technical support in
the running of the BIOX plant. |
A following static exchange rates have been applied and shown
in Table 19.2.
Table 19.2: Exchange Rates
Exchange |
Rate |
US$: ZAR |
18.74 |
US$: AUD |
1.50 |
US$: GBP |
0.79 |
US$: EUR |
0.92 |
The production profile is reported as plant feed fed to the
plant from four mineralization properties which are McCays, Isabella North, Isabella South and Bubi for all three scenarios that were
considered before selecting the one published in this report. A total of ~23 Mt of mineralized material is delivered to the processing
facility, with ~200 Mt of waste removed over the same period. The average grade over life of mine is estimated at ~2.38 g/t Au.
| 19.7 | Taxes, Levies and royalties |
The information below relates to the fiscal year 2023 and is
in Zimbabwe Gold (ZiG), unless otherwise stated. An appropriate exchange rate to the US$ will be applied at the time of any transaction.
The tax regime in Zimbabwe has remained relatively stable and
favorable over the past few years compared to other jurisdictions in the region.
Those taxes, royalties, duties etc, directly affecting the
mining industry are considered below.
| · | Royalties are levied on gross revenue from the sale of gold, |
| // | |
| · | Royalties are levied at source hence payments made by FGR (the entity that buys a portion of the gold
produced by Blanket Mine, another operating subsidiary of Caledonia) are net of royalties. To the extent that Bilboes exports 100% of
its production, an alternative collection mechanism for royalties will have to be agreed. |
| · | From 1 January 2020, mining royalties are an allowable expense in the determination of taxable income, |
| · | For primary gold producers a two-tier system that is based on gold prices is applicable. For gold prices
below US$ 1,200/oz the rate is 3% and for gold prices above US$ 1,200/oz the rate is 5%. |
| // | |
The following customs duties apply: -
· |
Maximum applied on cost of imports |
|
: 10% |
· |
Capital equipment imports |
|
: 0% |
· |
Value added taxes are applied as follows: - |
|
|
· |
Locally procured and imported inputs and equipment |
|
: 15% |
· |
Exports are zero rated and input Value Added Tax (VAT) is fully
recoverable in most cases or can be used to set off against other tax liabilities. No output VAT is levied on gold sales as they are
zero-rated. Silver is subject to VAT at 15%. |
The following withholding taxes apply:-
· |
Supplies by unregistered traders (without Tax Clearance Certificate) |
|
: 30% |
· |
Non-Resident Shareholders’ Tax on dividends* |
|
: 5 - 15% |
· |
On fees, royalties, dividends, and interest |
|
: 15% |
· |
Services from non-residents |
|
: 515% |
· |
Lower withholding taxes may be obtained in terms of double tax agreements. |
|
|
· |
*dividend payments to non-residents in countries with a Double Tax Agreement
with Zimbabwe (e.g., the United Kingdom) incur withholding tax at 10%. |
|
|
The following corporate taxes apply: -
· |
On taxable profits: 25% flat rate [plus 3% AIDS levy] to make effective rate 25.75%, |
· |
Capital redemption allowances in year incurred. |
|
: 100%, |
· |
Deduction limits on passenger vehicles |
|
:US$ 10,000, or ZiG equivalent at prevailing bank rates, |
· |
Deduction limits on employee housing |
|
: US$ 25,000, or ZiG equivalent at prevailing bank rates |
· |
Deduction limits on donations to medical centers: US$ 100,000 per annum, or ZiG equivalent at prevailing bank rates |
· |
Deduction limits on donations to research and development institutions :US$ 100,000 per annum, or ZiG equivalent at prevailing bank rates |
· |
Pre-production operating expenditure: 100% in first year of production |
· |
Carry forward of losses: Indefinite for mining operations. |
· |
Each mining location is ring fenced and
only costs applicable to that location are deductible. |
| // | |
The applicable Employment Levies are: -
· |
National Social Security |
|
: 4.5% of an employee wage rate. |
· |
The cap is declared monthly |
|
: ZiG 5 010.83 per month. |
· |
Workmen’s compensation |
|
: 1.77% base earnings |
· |
Manpower Development Levy |
|
: 1% of the gross earnings |
· |
Standards Development Levy |
|
: 0.5% of the gross earnings |
The appliable Electricity Levies are: -
· |
Rural Electrification Kevy of 6% of electricity bill |
The Rural Council Levies apply: -
· | Unit tax: ZiG 158.62 / unit, |
· | The number of units for each company is dependent on number of employees with the first 100 employees
making a unit and any other 50 employees thereafter forming units. |
The following taxes, levies or royalties apply: -
· | Administration fees in excess of 1% of other tax-deductible expenses are disallowed and taxed as a dividend. |
Capital gains tax (Table 19.3)
Table 19.3: Capital Gains Tax
Acquired |
Rate |
Currency |
Before 22 February 2019 |
5% of gross capital amount |
ZiG |
5% of foreign currency gross capital amount |
US$ |
On or after 22 February 2019 |
20% of capital gain |
ZiG |
20% of foreign currency capital gain |
US$ |
The following Capital gains withholding tax apply: -
· |
On listed marketable securities: |
|
1.5% |
· |
On listed marketable securities held for less than 6 months: |
|
4% |
· |
On unlisted marketable securities: |
|
5% |
· |
On immovable property acquired before 22 February 2019: |
|
5% |
· |
On immovable property acquired after 22 February 2019: |
|
15% |
| // | |
Note: In respect of any sale of a specified asset that is purported
to have been sold in ZiG, it shall be presumed that the specified asset was paid for in a foreign currency at the United Sates dollar
market valuation of the specified asset on the date of sale, and that the capital gains tax thereon shall be paid in United States dollars
accordingly, unless the seller provides documentary proof satisfactory to the commissioner of taxes that the specified asset in question
was sold for ZiG.
Deferment of VAT collection on imported capital equipment is
as per Table 19.4
Table 19.4: Vat Collection
Value of Equipment (US$) |
Deferment period (Days) |
100,000 to 1,000,000 |
90 |
1,000,001 to 10,000,000 |
120 |
10,000,001 and above |
180 |
Mining claims fees are based on land area. The Mines and Minerals
Act provides for maintenance of mining title through payment of annual protection fees. The protection fee for a gold / base metal block
is US$ 150 per 5 ha per annum. EPOs have a two to threeyear tenure and can be renewed for an additional period to a cumulative maximum
of six years subject to approval by the Ministry of Mines and Mining Development’s Mining Affairs Board and a renewal fee of US$
1,500 is required with the application. The annual rental fee US$ 0.08 per ha in the first year, US$ 0.11 in the second year and US$ 0.15
in the third year. A company is allowed to peg claims during the tenure of the EPO subject to the following conditions:
| · | That the area to be pegged is not prohibited from pegging under the Mines and Minerals Act after the acquisition
of a prospecting licenses at US$ 75 per gold / base metal block, |
| · | Appointment of an Approved Pegger for the requisite groundwork and filing of paperwork for registration, |
| · | Payment of registration fees of US$ 300 for a base metal block and US$ 563 for a special base metal block, |
| · | Approval by the Ministry of Mines for erection of permanent beacons around the blocks as per Mines and
Minerals Act, |
| · | EIA fees charged based on a sliding scale from 0.8% to 1.2% of the relevant project cost, |
| · | Payroll tax (Pay as You Earn) is deducted from employees’ earnings and paid to the government. The
tax-free band has been increased to ZiG 16,272 per annum or ZiG 1,356 per month. The upper income tax bands moved to ZiG 488 160 per annum
or ZiG 40,680 per month. The effective maximum rate of tax (including AIDS levy) is 41.2%. |
| · | Exemption of customs duty import tax and surtax on all capital goods during exploration phase of a mining
project and for a period of up to five years from date of grant of a mining title, during the development phase of the mining project. |
| // | |
| · | A 2% Intermediated Money Transfer Tax (IMTT) charged per e-commerce ZiG denominated transaction. Any transaction
exceeding equivalent in ZiG of US$ 500,000 has a maximum tax of US$ 10,150 (at the Interbank Rate) payable in ZiG. |
| · | IMTT (Outbound Foreign Payment Tax) at a rate of 2% for every outbound foreign payment or partial payment
made. This tax applies to each transaction that is subject to the tax thin capitalization regulations: offshore borrowings require Reserve
Bank of Zimbabwe approval, and interest paid on borrowings of a debt-to-equity ratio of up to a maximum of three to one is tax deductible.
Beyond the maximum allowable ratio any interest paid is assumed to be a dividend pay-out and is not tax deductible and is also liable
to withholding tax at the non-resident tax rate. |
The following tax rebates are allowed:
| · | Rebate of duty on goods for the prospecting and search for mineral deposits. |
| · | Rebate of duty on goods imported in terms of an agreement entered pursuant to a special mining lease. |
| · | Rebate of duty on goods imported temporarily for an approved project. |
| · | Rebate of duty on goods for incorporation in the construction of approved projects. |
| · | No export duties for all mineral commodities. |
| · | Rebate of duty extended to capital equipment imported by mining and manufacturing sectors for values above
US$1 million, effective 1 January 2016. |
| 19.8 | Capital Expenditure and Phasing |
The total initial capital estimate for the project includes
capital required to expand the mining operation and a contingency allowance.
Initial capital has been phased based on a high-level project
execution schedule for each scenario. Further detail covering the execution schedule and basis of costs can be found in the relevant section
of this report.
A summary of initial capital costs is shown in Table 19.5.
This is inclusive of mining, processing, tailings, and a contingency allowance.
Table 19.5: Initial Capital Cost –
Constant Terms (2023)
Scenario |
Unit |
Total |
FY
2025 |
FY
2026 |
FY
2027 |
FY
2028 |
FY
2029 |
FY
2030 |
FY
2031 |
FY
2032 |
FY
2033 |
FY
2034 |
FY
2035 |
FY
2036 |
Base
Case |
US$
m |
403 |
- |
120 |
189 |
24 |
- |
11 |
15 |
43 |
1 |
- |
- |
- |
| 19.9 | Stay in Business Capital |
SIB capital expenditure has been considered, covering both
mining and process plant allowances.
| // | |
Mining costs have been allowed for over LoM on a period basis
for fleet replacement. Process plant SIB has been based on an annual allowance of 1% of process plant OPEX. Total SIB costs are summarized
in Table 19.6
Table 19.6: SIB Capital Cost (LoM) –
Constant Terms (2023)
Scenario |
Unit |
Total (LoM) |
Base Case |
US$ m |
8.52 |
| 19.10 | Operating Expenditure |
The operating costs over the LoM include the mining operation,
processing plant (incl. tailings disposal) and G&A costs.
Table 19.7 shows the estimated operating cost by category over
the LoM. These costs have been developed from first principles and do not include a contingency.
Table 19.7: Operational Cost Estimate
(LoM) – Constant Terms (2023)
Description |
Unit |
Value |
Mining |
|
|
Cost |
US$ m |
596.13 |
Unit cost |
US$/t RoM |
25.54 |
Process Plant |
|
|
Cost |
US$ m |
564.31 |
Unit cost |
US$/t RoM |
24.18 |
G&A |
|
|
Cost |
US$ m |
47.17 |
Unit cost |
US$/t RoM |
2.02 |
Total |
|
|
Cost |
US$ m |
1,207.61 |
Unit cost |
US$/t RoM |
51.74 |
Process specific parameters have been applied for each mineralization
property, informed from historical test work outcomes, third party consultation and discussions with the Bilboes owners’ team.
Metal recoveries have been applied as static variables over
the prescribed LoM for each scenario. A summary of these inputs is shown in Table 19.8.
| // | |
Table 19.8: Gold Recovery per Mineralization
Property
Property |
Unit |
Recovery |
Reference |
McCays |
% |
83.62 |
Testwork / Third party / Client |
Isabella north |
% |
83.62 |
Testwork / Third party / Client |
Isabella south |
% |
83.62 |
Testwork / Third party / Client |
Bubi |
% |
88.88 |
Testwork / Third party / Client |
A static metal price, based on a three-year trailing average
price up to April 2024, has been applied as prescribed by the Bilboes owners’ team. A price of US$ 1,884/oz has been applied in
the financial model for all scenarios considered.
No allowance for asset disposal at the end of life of mine
has been included in the financial model.
No allowance for working capital has been included in the financial
model.
| 19.15 | Sunk and On-going Capital |
No on-going, historical, or sunk costs have been considered
in the financial model.
| 19.16 | Reclamation and Closure |
An allowance for on-going environmental rehabilitation is included
in the financial model together with a final closure cost of US$ 32 m expended during the last year of operation for each scenario. On-going
environmental rehabilitation is based on a unit rate of US$ 0.25/t RoM.
Royalty tax has been based on Zimbabwean legislation (Mines
and Minerals/Finance Act) and supported by the Bilboes owners’ team. Royalties’ payable are a function of gross revenue and
a royalty percentage. The royalty percentage is fixed at 5% for gold and enforced regardless of operating margin achieved. The formula
used to calculate royalty’s payable has been defined below:
𝑅𝑜𝑦𝑎𝑙𝑡𝑦
(𝑈𝑆𝐷) = 𝐺𝑟𝑜𝑠𝑠 𝑆𝑎𝑙𝑒𝑠 (𝑈𝑆𝐷)
× 𝑅𝑜𝑦𝑎𝑙𝑡𝑦 %
Where royalty % is defined as:
𝑅𝑜𝑦𝑎𝑙𝑡𝑦
% = 5% 𝑓𝑜𝑟 𝑔𝑜𝑙𝑑 𝑠𝑎𝑙𝑒𝑠
A net smelter royalty (NSR) of 1% has been applied for the economic analysis.
| // | |
| 19.18 | Corporate Income Tax |
Corporate income tax has been based on Zimbabwean legislation
(Income Tax Act) and as advised by the Bilboes owners’ team. Income tax payable is a function of pre-tax profit and a taxation rate.
Pre-tax profit is inclusive of all revenue, capital and development costs, operating costs, depreciation, amortization, and royalties.
Capital expenditure (and development costs) incurred prior to production are claimed in full during the first production year. Subsequent
capital expenditure is expended in full during the year of occurrence. Losses are carried over indefinitely until a profit is realized
following which tax is levied based on annual pre-tax profits. A fixed effective taxation rate of 25.75% has been applied and is inclusive
of an AIDs levy.
The project is based on an execution start date of 2026. A
10% discount rate has been applied in the financial model. A day zero discounting has been applied i.e. the full financial year of 2025
has not been discounted in the model.
The financial model has been prepared on a 100% equity project
basis and does not consider alternative financing scenarios (Table 22-8). A discount rate of 10% has been applied in the analysis. The
outcomes are presented on a pre-tax and post-tax basis. A static metal price of US$ 1,884/oz has been applied. All-in sustaining costs
have been reported as per the WGC guideline dated November 2018 and is exclusive of project capital, depreciation, and amortization costs.
Capital payback is exclusive of the construction period and referenced to the start of first production. Key financial outcomes are shown
in Table 19.9.
Table 19.9: Summary of Economic Outcomes
Description |
Units |
Value |
Production Statistics (LoM) |
|
|
Life of Mine |
years |
10 |
Total RoM Tonnes |
tonnes |
23,340,310 |
Cost Estimate Summary
(LoM)
Capital Cost (incl. contingency) |
US$ m |
402.97 |
SIB Capital Cost |
US$ m |
8.52 |
Operating Cost |
US$ m |
1,207.61 |
Unit Cost |
US$/t RoM
|
51.74
|
Revenue (LoM) |
|
|
Au Recovered |
Ozt |
1,518,111 |
Ave. Price |
US$/Ozt |
1,884 |
Financial Outcomes
(Pre-tax, Constant Model Terms)
NPV @ 10% |
US$ m |
431.68 |
IRR |
% |
39.39 |
Peak Cash Funding |
US$ m |
309.18 |
AISC |
US$/Ozt |
967.90 |
Payback (UNDISCOUNTED) - From Production Start |
years |
1.9 |
| // | |
Financial Outcomes
(Post-tax, Constant Model Terms)
NPV @ 10% |
US$ m |
308.73 |
IRR |
% |
33.99 |
Peak Cash Funding |
US$ m |
309.18 |
AISC |
US$/Ozt |
967.90 |
Payback (UNDISCOUNTED) -
From Production Start |
years |
1.9 |
| // | |
Table 19.10: Cashflow Model
|
|
FY 2025 |
FY 2026 |
FY 2027 |
FY 2028 |
FY 2029 |
FY 2030 |
FY 2031 |
FY 2032 |
FY 2033 |
FY 2034 |
FY 2035 |
FY 2036 |
FY 2037 |
Revenue |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Total metal produced |
koz |
- |
- |
- |
145.18 |
196.10 |
166.02 |
170.20 |
178.44 |
174.87 |
146.01 |
144.31 |
135.70 |
67.80 |
Net Revenue |
US$ m |
- |
- |
- |
266.64 |
360.17 |
304.91 |
312.59 |
327.72 |
321.18 |
268.16 |
265.05 |
249.22 |
124.53 |
Operating and Other Costs |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Mining costs |
US$ m |
- |
- |
- |
(58.53) |
(85.31) |
(91.60) |
(92.27) |
(47.97) |
(53.74) |
(56.22) |
(49.95) |
(46.96) |
(13.58) |
Process plant costs |
US$ m |
- |
- |
- |
(42.86) |
(50.51) |
(50.24) |
(50.24) |
(49.75) |
(70.79) |
(70.49) |
(70.49) |
(70.49) |
(38.78) |
G&A costs |
US$ m |
- |
- |
- |
(2.95) |
(4.91) |
(4.91) |
(4.91) |
(4.91) |
(4.91) |
(4.91) |
(4.91) |
(4.91) |
(4.91) |
Environmental Rehabilitation |
US$ m |
- |
- |
- |
(0.58) |
(0.72) |
(0.72) |
(0.72) |
(0.71) |
(0.55) |
(0.54) |
(0.54) |
(0.54) |
(31.90) |
Total |
|
- |
- |
- |
(104.92) |
(141.46) |
(147.47) |
(148.14) |
(103.34) |
(129.99) |
(132.17) |
(125.90) |
(122.91) |
(89.17) |
SIB Capital |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Mining |
US$ m |
- |
- |
- |
- |
- |
- |
- |
(2.88) |
- |
- |
- |
- |
- |
Process plant |
US$ m |
- |
- |
- |
(0.43) |
(0.50) |
(0.50) |
(0.50) |
(0.50) |
(0.71) |
(0.70) |
(0.70) |
(0.70) |
(0.39) |
Total |
US$ m |
- |
- |
- |
(0.43) |
(0.50) |
(0.50) |
(0.50) |
(3.37) |
(0.71) |
(0.70) |
(0.70) |
(0.70) |
(0.39) |
Capital Expenditure |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Mining |
US$ m |
- |
- |
(10.91) |
(14.63) |
- |
- |
- |
- |
- |
- |
- |
- |
- |
Process and Infrastructure |
US$ |
- |
(103.60) |
(141.00) |
(4.00) |
- |
(10.91) |
(13.89) |
(37.24) |
(1.18) |
- |
- |
- |
- |
Indirect |
USD |
- |
(11.53) |
(15.17) |
(2.87) |
- |
- |
(0.74) |
(1.48) |
- |
- |
- |
- |
- |
Contingency |
USD |
- |
(4.83) |
(22.14) |
(2.52) |
- |
- |
(0.52) |
(3.81) |
- |
- |
- |
- |
- |
Total Capital |
USD |
- |
(119.96) |
(189.22) |
(24.02) |
- |
(10.91) |
(15.15) |
(42.53) |
(1.18) |
- |
- |
- |
- |
Royalties |
US$ m |
- |
- |
- |
(13.67) |
(18.47) |
(15.64) |
(16.03) |
(16.81) |
(16.47) |
(13.75) |
(13.59) |
(12.78) |
(6.39) |
Pre-Tax Cash Flow |
US$ m |
- |
(119.96) |
(189.22) |
123.60 |
199.73 |
130.39 |
132.77 |
161.68 |
172.83 |
121.53 |
124.85 |
112.83 |
28.58 |
Tax |
US$ m |
- |
- |
- |
- |
(3.64) |
(33.58) |
(34.19) |
(41.63) |
(44.50) |
(31.30) |
(32.15) |
(29.05) |
(7.36) |
Post-Tax Cash Flow |
US$ m |
- |
(119.96) |
(189.22) |
123.60 |
196.09 |
96.82 |
98.59 |
120.05 |
128.33 |
90.24 |
92.70 |
83.78 |
21.22 |
| // | |
| 19.22 | Sensitivity Analysis |
A sensitivity analysis has been conducted assessing the impact
of variations in initial capital cost, operating cost, and metal selling price. Each variable is assessed in isolation to determine the
impact on Net Present Value (NPV) and Internal Rate of Return (IRR).
The impact of initial capital costs has a limited elasticity
in impacting overall project value due to the capital phasing profile and relatively low expenditure in comparison to revenue and operating
costs over the prescribed LoM. A summary of these relative variations is shown in Figure 19-1
Figure 19-1 Sensitivity Analysis
A data table analysis has been conducted to specifically illustrate
the influence of changes in gold pricing and discount rates on the project's economic outcomes and is presented (bold) in Table 19.11
that indicates the current base case scenario. The NPV and payback period (undiscounted, from production start) are presented on a post-tax
basis.
| // | |
Table 19.11: Data Table Analysis
|
Discount Rate (%) |
|
Gold Price (USD/oz) |
15% |
12.5% |
10% |
7.5% |
5% |
Payback Period (Post-tax), years |
NPV (Post-tax), USD M |
1,500 |
31 |
59 |
94 |
137 |
191 |
3.6 years |
1,700 |
116 |
157 |
206 |
267 |
342 |
2.5 years |
1,884 |
194 |
246 |
309 |
385 |
480 |
1.9 years |
2,000 |
243 |
302 |
373 |
460 |
567 |
1.8 years |
2,200 |
327 |
398 |
484 |
588 |
717 |
1.6 years |
2,400 |
411 |
494 |
594 |
717 |
867 |
1.5 years |
2,600 |
495 |
590 |
705 |
845 |
1016 |
1.3 years |
| // | |
Several small mines and two larger ones have operated in the
past in the area around the Isabella property and within the Isabella and Gwizaan EPOs (Figure 20-1) but all of these had been dormant
for at least 15 years prior to the renewal of exploration activity in the area in the early 1980s. The productions listed in Table 20.1
are for the period to 1980. The Calcite Mine is located in the area now covered by the Isabella operation and its production is included
in the History section. The Motapa, Fossicker and Jupiter Mines are situated immediately to the south of the Mine and trend in the same
general strike of Isabella, McCays and Bubi.
The Isabella EPO 1726 surrounds Isabella McCays while the Gwizaan
EPO 1646 surrounds Bubi as well as a cluster of other Bilboes exploration claims namely When, Sandy and Ferroro. The two EPOs which are
contiguous were approved for exploration through a government gazette of 13 July 2018 and had a combined ground holding of 67,419 ha.
The EPOs have a three-year tenure which expired on 12 July 2021. Approvals for extension of the tenure of the EPOs are still pending.
Several high quality geological and aeromagnetic targets are located within the major northeast-southwest trending deformation zones that
transect the EPOs such as along the Peter-Pan, Courtleigh and Gabriella-Mulungwane shear zones. These targets in addition to the existing
exploration claims offer potential for organic growth of Bilboes’ Gold Mineral Resources.
| // | |
Figure 20-1: Adjacent Properties
around Isabella McCays and Bubi
| // | |
Table 20.1: Historic Gold Production
from Mines around Isabella McCays and Bubi to 1980
Mine |
Au kg |
Grade g/t |
Coordinates |
Locality from Isabella |
Easting |
Northing |
Motapa |
9,467 |
4.3 |
663,613 |
7,844,250 |
2 km south |
Fossicker |
472 |
3.7 |
664,953 |
7,844,803 |
3 km south-east |
Jupiter |
201 |
3.9 |
663,870 |
7,846,633 |
1 km east |
Lonely |
34,786 |
17.5 |
683,276 |
7,841,837 |
20 km east |
Peter Pan |
968 |
2.9 |
680,606 |
7,846,618 |
18 km east |
Robin Hood |
248 |
2.1 |
677,790 |
7,848,663 |
15 km east |
Tiberius |
263 |
2.2 |
679,408 |
7,842,128 |
17 km east |
Source Bartholomew (1990), Coordinate system: UTM, Arc1950,
Zone 35S, Spheroid-Clarke 1880.
Gold mining near Bulawayo, Zimbabwe, involves several projects
currently being developed by various companies.
One significant project is the Bulawayo Gold Project, led by
Galileo Resources. This project encompasses two exploration licenses covering 1,300 km2 near Bulawayo. Recent soil surveys
have revealed substantial gold targets, extending known gold-bearing structures in the region. The project aims to identify and drill-test
these anomalies, which have shown promising goldin-soil sample results.
Additionally, Galileo Resources is also involved in the Queen's
Mine area near Bulawayo. They have identified multiple gold targets based on recent soil analytical results. These targets represent extensions
of existing gold-bearing structures, which host both commercial and artisanal mining operations.
Another notable venture is the Golden Valley Project, acquired
by Pambili in November 2023. Located in Matabeleland Province, this project has a history of high-grade underground mining. Pambili plans
to leverage modern exploration techniques to unlock the full potential of the site, which has been underexplored in recent years.
The QP has been unable to verify the information in this section.
The information in this section is not necessarily indicative of the mineralization on the Bilboes properties.
| // | |
| 21 | OTHER RELEVANT DATA AND INFORMATION |
None.
| // | |
| 22 | INTERPRETATION AND CONCLUSIONS |
| 22.1 | Mineral Resource Estimate |
| · | The data collected during the exploration, drilling and sampling programmes, including surveying, drill
hole logging, sampling, geochemical analysis, and data quality assurance, was collected in a professional manner and in accordance with
appropriate industry standards by suitably qualified and experienced personnel. |
| · | The geological modelling and Mineral Resource estimate were undertaken utilizing recognized deposit and
industry strategies/methodologies for the Bilboes deposit. |
| · | The Mineral Resource is constrained in an optimized pit shell. This together with the assumptions relating
to mining, processing, infrastructure, and market factors supports the “reasonable prospects for eventual economic extraction”. |
| · | Based on an assessment including: - data quality and integrity, data spacing, confidence in the grade
interpolation, confidence in the geological interpretation and confidence in the estimate the QP believes the Mineral Resource estimate
is robust. |
| · | Both the modelling and the grade interpolation have been conducted in an unbiased manner and that the
resulting grade and tonnage estimates should be reliable within the context of the classification applied. |
| · | The open pit modelling is based on suitably supported assumptions and parameters and completed utilizing
appropriate industry standards suitable for the Bilboes Project. |
| · | The economic modelling is supported by technical studies in mining, processing, infrastructure, environmental,
social, and marketing. Based on the inputs from these disciplines, the financial model demonstrates an economically viable mine. The economic
analysis is based on a US$ 1,884/oz. |
| · | The sensitivity analyses demonstrates that the profitability of the project is most sensitive to revenue
related factors such as gold price and recovery. |
The financial model has been prepared on a 100% equity project
basis and does not consider alternative financing scenarios. A discount rate of 10% has been applied in the analysis. The outcomes are
presented in Table 22.1 on a post-tax basis. A static metal price of US$1,884/oz has been applied.
| // | |
Table 22.1: Project Economics Summary
Description |
Unit |
Value |
Financial Outcomes (post Tax, Constant Model Terms) |
|
|
NPV @ 10% |
US$ m |
308.73 |
IRR |
% |
33.99 |
Peak Cash Funding |
US$ m |
309.18 |
AISC§§ |
US$/oz |
967.90 |
Payback (UNDISCOUNTED) - From Production Start |
years |
1.9 |
Various risks have been identified with consideration of the
appropriate mitigating factors.
These are presented in Table 25-2.
| // | |
Risk Category |
Risk |
Description / Cause |
Mitigation / Control |
Permitting |
Significant effect of ability to produce |
The lapsing of permits or license |
Proactive management of permits, licenses, compliance etc. |
Geology and Mineral Resources |
Significant Variance in
Mineral Resource Tonnage |
Inaccurate mineral resource
models due to poor geological understanding of the deposit.
Inaccurate mineral resource
models due to geological complexity of the deposit.
The tonnage is expected
to change on a local scale but is unlikely to vary significantly on a global scale.
|
Contingency measures applied during
mineral resource modelling to ensure mineral resource models remain conservative.
Continued drilling conducted on the
deposit to improve geological understanding of the deposit.
A infill drilling programme will be
conducted pre-mining and throughout the life of the mine.
|
Geology and Mineral Resources |
Significant Variance in Mineral Resource Grade |
The estimation of the grade is based on a limited number of intersection points. Although care has been taken to provide a robust estimate, the grade is expected to change on a local scale but is unlikely to vary significantly on a global scale. |
A grade control programme including
drilling will be conducted pre-mining and throughout the life of the mine.
Provision has been made for infill
drilling and on-going exploration drilling during LoM.
|
Geology and Mineral Resources |
Inaccurate oxide, transitional and sulphide plant feed tonnes and grades |
Poor interpretation of the oxide, transitional and sulphide zones resulting in non-optimal planning. |
Continued monitoring of the Oxide-Sulphide interface during the mining operation. |
Mining |
Poor run of mine plant feed grade |
Poor grade control of the RoM plant feed resulting in excessive dilution of the grades. |
1. Grade control drilling will be conducted pre-mining and the cost for this has been allowed for in the IA.
2. Grade controllers will be employed to monitor the mining team during operations.
|
Mining |
Significant reduction in plant feed produced |
Lack of production due to aspects of geology, personnel, and resources |
3. Continuous skills training
4. Monitoring of critical resources of production e.g. fleet
5.
Proactive production management
|
| // | |
Processing |
Lower than planned gold recovery from the plant |
Inaccurate gold recovery from the plant |
Gold recovery assumptions
were informed by the onsite flotation and BIOX® pilot plant test work.
Bilboes procured a flotation
and a BIOX pilot plant for on-site test works during the operational phase to optimize the flotation and BIOX® gold recovery.
Sulphide / Sulphur concentrate
feed grade which ensures high bacterial activity and process stability is higher than the minimum of 4-6% required.
|
| // | |
Based on the study work completed it shows a positive economic
outcome. It is recommended that the Bilboes Project enters a feasibility study phase. The anticipated cost of the proposed feasibility
study is $1,429,000.
| // | |
| · | Bartholomew DS (1990) Gold Deposits in Zimbabwe. Geological Survey of Zimbabwe Mineral Resources Series,
23, pp 75 |
| · | Bieniawski, ZT (1976). Exploration for Rock Engineering. Proceedings of the Symposium on Exploration for
Rock Engineering, Johannesburg, 1-5 November 1976 Volume 1 |
| · | Bieniawski, ZT (1989). Engineering Rock Mass Classifications. A Complete Manual for Engineers and Geologists
in Mining, Civil, and Petroleum Engineering. John Wiley and Sons. 251pp |
| · | Burger, J., Knight, J. W., Visser, F. J., Warschkuhl, O. W., & Obermeyer, P. G. (2017). Bilboes Preliminary
Assessment. |
| · | Gore J, James DE, Zengeni TG, Gwavav O (2009). Crustal structure of the Zimbabwe Craton and the Limpopo
Belt of Southern Africa: New constraints from seismic data and implications for its evolution. South African Journal of Geology 112(3-4):213-228 |
| · | Mukaka SB, Wilson AH, Carlson RW (1998). A multielement geochronologic study of the Great Dyke, Zimbabwe:
significance of the robust and reset ages. Earth and Planetary Science Letters, Volume 164, Issue 1-2, p. 353-369. |
| · | Mugandani, F (unknown). Overview Of Zimbabwe’s Mineral Resource Potential – Tip Of The Iceberg?,
Zimbabwe Geological Survey |
| · | Mugandani, ET (2017). Status of Mineral Exploration and Development in Zimbabwe. SAIMM Conference, 03
August 2017 |
| · | Ngilazi, A., and Martin, A. (2017). Independent Technical Report on Bilboes properties, Matabeleland,
Zimbabwe. Technical Report, Bilboes Holdings (Pvt) Ltd. |
| · | SLR Consulting (Pty) ltd (August 2019) Hydrogeological Study for Bubi-Isabella-McCays |
| · | Mines. Project No.: 710.04026.00019. Prepared for: DRA Projects (Pty) Ltd |
| · | SLR Consulting (Pty) ltd (August 2019) Geotechnical Study for Bubi-Isabella-McCays Mines. Project No.:
710.04026.00019. Prepared for: DRA Projects (Pty) Ltd |
| · | World Gold Council (2018) Guidance Note on Expenditure Definitions ➢
World Gold Council (2024) Statistics for Gold Demand and Supply |
| // | |
| 25 | RELIANCE ON INFORMATION PROVIDED BY THE REGISTRANT |
The following chart identifies the categories of information
for which the QP has relied on information provided by Bilboes and the particular portions of the TRS that were prepared in reliance upon
such information and the extent of such reliance.
| · | Geological Data (drilling, assays etc.) and Exploration Information, |
| · | Metallurgical test work reports, |
| · | Processing labour rates, unit power costs and unit reagent costs delivered to site, |
| · | General and administrative costs, |
| · | Maro variables covering exchange rates and gold pricing (including refining), |
| · | General economic input variables, taxation and levy rates, |
| · | Geotechnical Studies where completed by SLR, |
| · | The Tailings Storage Facility design and costing was also completed by SLR. |
The sections where reliance has been placed on this information
has present in Table 25.1.
Table 25.1: Sections where information/data
from the Registrant has been relied upon
Land title and tenure information |
Section 4 |
Geological Data (drilling, assays etc.) and Exploration Information, |
Section 6,7,8 |
Metallurgical test work reports, |
Section 10 |
Processing labor rates, unit power costs and unit reagent costs delivered to site, |
Section 18,19 |
General and administrative costs, |
Section 19 |
Maro variables covering exchange rates and gold pricing (including refining), |
Section 19 |
General economic input variables, taxation and levy rates, |
Section 19 |
Environmental and Social Studies |
Section 17 |
Geotechnical Studies where completed by SLR, |
Section 13 |
The Tailings Storage Facility design and costing was also completed by SLR. |
Section 15 |
The QP affirms that the inputs mentioned above which have been
supplied by other sources meet an acceptable standard, drawing from relevant sources derived from prior experience, current applicable
operations and/or applicable benchmarks/studies.
The QPs believes such reliance is reasonable after the data/information
has been reviewed.
Page 179 of 179
Exhibit 99.2
CONSENT OF DRA PROJECTS (PTY) LTD.
December 16, 2024
DRA Projects (Pty) Ltd.
United States Securities and Exchange Commission
Ladies and Gentlemen:
| | Re: Caledonia Mining
Corporation Plc (the “Company”) |
DRA Projects (Pty) Ltd. hereby consents to:
| (1) | the
inclusion in this Form 6-K of references to the undersigned’s name in connection with
the technical report summary titled “Bilboes Gold Project Technical Report Summary”
with an effective date of May 30, 2024, or extracts and information therefrom contained in
the Company’s Form 6-K dated December 16, 2024 (the “Technical Information”)
filed with the United States Securities and Exchange Commission (the “SEC”);
and |
| (2) | the
filing of this consent under cover of this Form 6-K with the SEC and of the incorporation
by reference of this consent, the use of the
undersigned’s name and the Technical Information into the Company’s Registration
Statement on Form F-3 (No. 333-281436), and any
amendments thereto, filed with the SEC. |
|
DRA Projects (Pty) Ltd. |
|
|
|
|
By: |
/s/ Tertius van Niekerk |
|
Name: |
Tertius van Niekerk |
|
Title: |
Senior Vice
President Mining |
|
DRA Projects (Pty) Ltd. |
|
|
|
|
By: |
/s/ Alistair Hodgkinson |
|
Name: |
Alistair Hodgkinson |
|
Title: |
Chief Operating Officer |
Exhibit 99.3
CONSENT OF EXPERT
December 16, 2024
Caledonia Mining Corporation Plc
United States Securities and Exchange Commission
Ladies and Gentlemen:
| | Re: Caledonia Mining
Corporation Plc (the “Company”) |
I, Craig Harvey, do hereby consent to:
| (1) | the inclusion in the Form 6-K dated November 11, 2024 of references to my name in
connection with the scientific and technical information contained in the Company’s news release dated November 11, 2024 announcing
the results from exploration at the Motapa Gold Project (the “Technical Information”) filed with the United States Securities
and Exchange Commission (the “SEC”); and |
| (2) | the filing of this consent under cover of this Form 6-K with the SEC and of the
incorporation by reference of this consent, the use of my name and the Technical Information
into the Company’s Registration Statement on Form F-3 (No. 333-281436), and any amendments
thereto, filed with the SEC. |
|
By: |
/s/ Craig Harvey |
|
|
Craig Harvey |
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