This technical report presents the updated mineral resource estimate and processing framework for the Bibiani Gold Mine, Ghana, as at 31 December 2023.
Report context
The Bibiani Gold Mine is owned and operated by Mensin Gold Bibiani Limited, a wholly owned Ghanaian subsidiary of Asante Gold Corporation. The effective date of this technical report is 31 December 2023, with an issue date of 30 April 2024. The Ghanaian Government holds a 10% non-equity free carry interest in the mine. This report supersedes the earlier NI 43-101 Technical Report with effective date 28 February 2022.
Processing route
Overall process design
The Bibiani processing plant is a 3.0Mtpa refurbished conventional carbon-in-leach (CIL) milling and processing facility. The plant achieved approximately 85% gold recovery during the 2022 to 2023 operating period. A phased expansion to 4.0Mtpa is planned from 2026. A schematic process flowsheet indicates current and phased additions, including a future flotation circuit and concentrate regrind, as well as an intensive concentrate leach and adsorption circuit.
Phase 1A plant modifications
Phase 1A modifications to the existing conventional CIL circuit included installation of a crusher, a PSA oxygen plant, and a Mach shear reactor. These modifications were completed before the 2022 plant start-up. Plant operations performance data for Phase 1A show the impact of the oxygen plant and online Mach reactor on peroxide consumption and dissolved oxygen levels. Dissolved oxygen levels were recorded before and after Mach reactor installation. The CIL tank 1 dissolution rate and dissolved oxygen levels were also monitored. Phase 1A milled tonnes per month versus plant availability and pit ore blend are documented.
Phase 1B key process design criteria
Phase 1B key process design criteria were sourced from Lycopodium 1997 and from Mining Process Project Engineering 2021. The schematic flowsheet of the future flotation circuit includes concentrate regrind, and the intensive concentrate leach and adsorption circuit is shown separately.
Key reported parameters
| Parameter | Value | Unit | Basis |
|---|---|---|---|
| Plant capacity (current) | 3.0 | Mtpa | Design (refurbished) |
| Plant capacity (planned) | 4.0 | Mtpa | Proposed design from 2026 |
| Gold recovery (conventional CIL, 2022-2023) | ~85 | % | Actual operating data |
| Main Pit sulphide ore treatment overall recovery (declared) | 92.0 | % | Testwork (2015 ALS variability) |
| Russell Pit sulphide ore treatment overall recovery (average normalised) | 90.2 | % | Testwork (2023 Intertek preliminary) |
| Main Pit high-grade sample sulphide flotation+leach recovery | 93.1 | % | Testwork (2023 Intertek preliminary, no gravity) |
| Main Pit high-grade sample direct cyanide recovery (P80 75µm) | 86.6 | % | Testwork (2023 Intertek preliminary, no gravity) |
| Main Pit variability CIL on gravity tails (average) | 71.5 | % | Testwork (2015 ALS Phase 2) |
| Main Pit gravity recovery (average, 14 variability samples) | 34 | % | Testwork (2015 ALS Phase 2) |
| Main Pit ALS variability overall gold recovery (range) | 85.1 – 92.6 | % | Testwork (2015 ALS, normalised, no gravity) |
| Main Pit ALS variability overall gold recovery (average) | 89.1 | % | Testwork (2015 ALS, normalised, no gravity) |
Project website: https://www.asantegold.com/operations/bibiani
Technical qualifications
The metallurgical test work reported for the Main Pit and Russell Pit is described as preliminary. The two Main Pit composite samples taken from stockpiles by geologists are noted as not representative of the ore body. A gravity gold recovery step was not included in the 2015 ALS Phase 1 and Phase 2 variability test work, and the declared 92.0% overall recovery for Main Pit sulphide ore treatment includes an additional 2.9% for the excluded gravity extraction step. The 2023 Intertek test work programs also did not include gravity gold recovery tests. The report states that the 2015 ALS test work results have been used as definitive for this study.
Source: NI 43-101 Technical Report and Updated Mineral Resource Estimate, Mensin Gold Bibiani Limited, Ghana, West Africa, effective 31 December 2023, issue date 30 April 2024, Sections 13, 17.
Consolidated report summaries
The following former standalone pages about this operation were consolidated here on October 25, 2026. They are retained for source traceability; dates and figures reflect each report’s own effective date and may be superseded by the current information above.
Bibiani Plant Evolution: Sulphide Circuit Commissioned, Crusher Expansion on Schedule
Asante Gold's Bibiani plant in Ghana has commissioned a new sulphide treatment circuit and is advancing a three-stage crusher expansion designed to lift throughput to 4.5 Mtpa.
The Bibiani Gold Project is an operating mine located in Ghana, West Africa, owned by Asante Gold Corporation. The processing facility, known as the Bibiani Plant, currently operates with a nominal design capacity of 2.4 Mtpa, employing a SAG/ball mill comminution circuit followed by a conventional carbon-in-leach (CIL) process for gold extraction. The operation was re-commissioned in June 2022 after a refurbishment period, and the most recent major modification was the commissioning of a sulphide treatment plant in Q4 2025, which was added to process gold from sulphide ores. Further modifications to the crushing, gravity, and leaching circuits are scheduled for 2026 to increase throughput capacity and improve recovery.
Critical Data
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Plant Design Throughput | 2.4 | Mtpa | Original plant design; current operational capacity. |
| Future Plant Throughput | 4.5 | Mtpa | Design capacity for the System 3 crusher plant. |
| Average Monthly Throughput (2023) | 191 | ktpm | Plant performance data. |
| Average Monthly Throughput (2024) | 195 | ktpm | Plant performance data. |
| Average Monthly Throughput (2025 YTD) | 190 | ktpm | Plant performance data. |
| Design Plant Throughput | 200 | ktpm | Design nameplate capacity for monthly throughput. |
| Crusher Plant Availability (Design) | 91.3 | % | Lycopodium 1997 Process Design Criteria. |
| Milling Plant Availability (Design) | 91.3 | % | Lycopodium 1997 Process Design Criteria. |
| Average Crusher Plant Effective Utilisation (2025) | 29.13 | % | Plant performance data. |
| Average Milling Plant Effective Utilisation (2025) | 79.56 | % | Plant performance data. |
| Cyclone Overflow Size, P80 | 75 | µm | Mill product size target. |
| Gold Head Grade (Design) | 3.90 | g/t Au | Lycopodium 1997 Process Design Criteria. |
| Gravity Gold Recovery (Design) | 31.0 | % | Lycopodium 1997 Process Design Criteria. |
| Leaching Gold Recovery (Design) | 87.0 | % | Without gravity, Lycopodium 1997 Process Design Criteria. |
| Sulphide Treatment Plant Throughput | 0.35 | Mtpa | Design capacity as concentrate feed. |
| Flotation Au Recovery (Design) | 89.6 | % | Phase 1B Process Design Criteria. |
| Concentrate Leach Au Dissolution (Design) | 88.4 | % | Phase 1B Process Design Criteria. |
| System 3 Crusher Plant Availability | 91.3 | % | Design criterion for new crusher plant. |
Overview
The Bibiani processing facility is a conventional gold plant that has been adapted to handle increasingly complex ore feed. The original design, established in 1997 by Lycopodium, featured a SAG mill and ball mill circuit with a standard CIL plant for gold recovery. Under Asante Gold's management, the plant was refurbished in Q3 2021, which included adding a gravity concentration circuit and re-conditioning the primary gyratory crusher. The plant was re-commissioned in June 2022.
Operational data from 2023 through 2025 shows the plant has consistently operated below its design throughput of 200 ktpm, with average monthly throughput of 191 ktpm, 195 ktpm, and 190 ktpm, respectively. The 2025 year-to-date figures extend through October 2025. Plant availability and utilisation are key constraints, with crusher and milling effective utilisations averaging 29.13% and 79.56% respectively in 2025, both below industry standards. Grid power supply interruptions are cited as the major cause of mill downtime, combined with primary gyratory crusher mechanical failures and the absence of surge capacity between the crusher and the mill.
The plant's response to these challenges has been a phased modification program. The first major change was the commissioning of the sulphide treatment plant in Q4 2025, followed by the construction of a new three-stage crusher plant (System 3) scheduled for 2026. Future upgrades to the gravity circuit and CIL plant are also planned.
Key Process Stages
The existing plant processes ore through a re-conditioned FLS 42 x 70 gyratory crusher for primary crushing. The crushed ore feeds a primary SAG mill and a secondary ball mill with classification hydrocyclones. A gravity concentration circuit using one Knelson XD48 concentrator and a Gekko ILR captures coarse gold, with the balance of the ore reporting to the conventional CIL circuit. The CIL section is followed by carbon elution and regeneration, a gold room with electrowinning, and reagent mixing.
The new sulphide treatment circuit, commissioned in October 2025, is designed to extract gold from sulphide ores. The circuit consists of scavenger flotation on the mill product stream, followed by ultra-fine regrinding of the concentrates in a vertical mill using ceramic media. Concentrate thickening is followed by intensive cyanidation in separate tank stages. The leached concentrate reports to carbon-in-pulp contactor tanks, with reagents mixed on site.
The future System 3 crusher plant is designed to replace the mobile crushers currently in use and to provide additional comminution capacity. The plant will feature a primary jaw crusher fed by a vibrating grizzly feeder, a secondary cone crusher, and tertiary crushers including two impactors and a cone crusher in closed circuit with screens. The system will produce a feed size of 100% passing 33 mm to the SAG mill, which is expected to support a throughput of 4.5 Mtpa. The current mill throughput from the mobile crushers is 400 tph, with simulations indicating that a feed size of 80% passing 25 mm would achieve the 4 Mtpa target.
Additional Interesting Data and Summary
Design criteria from the original Lycopodium 1997 work show a design head grade of 3.90 g/t Au and expected leach gold recovery of 87% without the gravity circuit. The existing plant design assumes a cyclone overflow P80 of 75 µm, a leach time of 24 hours, and a leach tails solution grade of 0.010 g/m³ Au. The design sodium cyanide addition is 0.75 kg/t material, and lime addition is 0.50 kg/t material.
The Phase 1B sulphide treatment design includes a flotation residence time of 15 minutes and a design mass pull of 8%. The intense leach circuit is designed for a pre-oxidation residence time of 1.5 hours at 20 ppm dissolved oxygen, followed by a cyanide leach residence time of 4.8 hours. The design concentrate gold dissolution is 88.4%, with carbon loadings of 1,000 g/t in the adsorption circuit.
Mill power consumption varies with the ore blend. Blends with a higher proportion of softer oxide ore consume less than 18 kWh/t. As the fresh ore proportion increases, power consumption rises to over 20 kWh/t, peaking at 24 kWh/t. This higher energy demand reduces milling throughput when targeting the P80 of 75 µm.
Operational data from February 2025 to October 2025 shows gold recovery fluctuated between approximately 75.8% and 78.9%. The head grade varied from 0.83 g/t to 1.41 g/t over the same period, with mill power ranging between 13.53 kWh/t and 23.75 kWh/t.
A notable operational constraint is the low crusher plant utilisation. The 2025 average was 29.13%, with several months recording zero utilisation. The report notes that mobile crushers have been used since October 2024 to maintain plant throughput above 150 ktpm.
The future modifications include a gravity circuit change in Q1 2026, with a new scalping screen on the cyclone underflow feed and a new additional Knelson concentrator. The CIL plant will also be modified in Q2 2026, converting the first CIL tank to a pre-leach tank and installing an Aachen shear reactor pumping system.
Key Processes
- Comminution: Gyratory crusher for primary crushing, followed by SAG mill and ball mill with hydrocyclone classification.
- Gravity Concentration: Knelson XD48 concentrator and Gekko ILR for gravity-recoverable gold.
- Flotation: Scavenger flotation cells on the mill product stream for sulphide ore treatment.
- Ultra-fine Regrinding: Vertical mill using ceramic media for scavenger concentrates.
- Intensive Cyanidation: Shear reactor pre-oxidation and pre-leaching stages followed by carbon-in-pulp contactors.
- Carbon-in-Leach: Conventional CIL circuit for gold leaching and adsorption.
- Elution and Regeneration: Carbon stripping and regeneration for cyanide recovery.
- Electrowinning: Gold recovery from concentrated solutions in the gold room.
Source: NI 43-101 Technical Report and Updated Mineral Resource Estimate, Asante Gold Bibiani Ltd., Ghana, West Africa, 31 December 2025. Project website: Bibiani Gold Project
