Overview
Nestled in the mineral-rich Kédougou Region of southeastern Senegal, the Diamba Sud Gold Project represents a significant and strategic development for mid-tier producer Fortuna Mining Corp. With an effective date of October 2025, this advanced-stage project is poised to become a cornerstone asset, leveraging a robust and well-understood mineral processing strategy to unlock economic value from a substantial gold resource. The project is designed to process both oxide and fresh (sulphide) material sourced from open-pit mining operations, targeting an average annual throughput of 2.0 to 2.5 million tonnes. This operational flexibility is key to managing the Life of Mine (LOM) feed schedule, which transitions from predominantly oxide material in the early years to a fully fresh ore feed later in the project’s life. The mineralization at Diamba Sud is characterized as free-milling with a very low proportion of gold locked in sulphides, making it highly amenable to conventional cyanidation treatment—a factor that simplifies the flowsheet and enhances project economics. Fortuna’s commitment to advancing Diamba Sud underscores its growth strategy in West Africa, a region renowned for its world-class gold deposits. The project’s technical design, detailed in a comprehensive report prepared by Fortuna’s senior technical team and external consultants, reflects a focus on simplicity, robustness, and operational efficiency, aiming to deliver strong gold recovery and sustainable production for years to come.
Key Process Stages
The Diamba Sud processing plant is engineered as a continuous, high-capacity operation following a classic gold recovery flowsheet. The design philosophy emphasizes reliability and ease of operation, incorporating modern control systems and equipment selections based on extensive metallurgical testwork. The circuit is designed to handle variable ore blends while maintaining target grind sizes and leach efficiencies. Below is a detailed breakdown of the primary process stages from run-of-mine (ROM) ore to gold doré bar production.
- Stage 1: Primary Crushing & Stockpiling: ROM ore with a maximum size of 900 mm is delivered to an adjacent pad. A front-end loader feeds a 162-tonne ROM bin, which discharges via an apron feeder to a primary single-toggle jaw crusher (C150 equivalent). The crusher reduces the ore to a suitable size for grinding. The crushed product is conveyed to a large, conical crushed ore stockpile with a total capacity of 19,000 tonnes, providing a crucial buffer (up to 76 hours of fresh feed) between mining and processing operations. Lime for pH control is added directly to the mill feed conveyor from a dedicated 100-tonne silo.
- Stage 2: Grinding & Classification (Single-Stage SAG Mill): Based on comminution testwork and modelling by Orway Mineral Consultants, a single-stage Semi-Autogenous Grinding (SAG) mill circuit was selected. An 8.53m diameter by 5.77m EGL SAG mill, powered by a 7.1 MW drive, receives feed from the stockpile. It operates with a 10-15% ball charge and a variable speed drive to adapt to changing ore characteristics. Mill discharge is screened, with undersize slurry pumped to a cluster of classifying cyclones. The cyclones produce a target overflow grind size of P80 106 µm for fresh ore (finer for oxides) for leaching, while the coarse underflow recirculates to the SAG mill at a designed circulating load of 333%.
- Stage 3: Gravity Recovery & Pre-Leach Thickening: To capture coarse, free gold early in the process, a gravity circuit treats a portion of the cyclone underflow. The slurry passes over scalping screens before feeding two 30-inch batch centrifugal concentrators. These units produce a high-grade concentrate, which is directly treated in an Intensive Leach Reactor (ILR) located in the gold room. Meanwhile, the cyclone overflow (the fine grind product) is sent through trash screens and into a leach feed thickener. This thickener increases slurry density to ~45% solids, optimizing conditions for the subsequent Carbon-in-Leach (CIL) circuit and reclaiming process water for reuse.
- Stage 4: Leaching & Adsorption (CIL Circuit): This is the heart of the gold dissolution and recovery process. Thickened slurry enters a train of seven large CIL tanks (each 12m diameter x 14m high), providing a total residence time of 24 hours. Cyanide and oxygen are added to the first tanks to dissolve the gold. Activated carbon, continuously moved counter-current to the slurry flow in the last six tanks, adsorbs the dissolved gold. Loaded carbon is removed from the second tank via a recessed impeller pump and screened out of the circuit. The now barren slurry (tailings) is pumped to the Tailings Storage Facility (TSF).
- Stage 5: Elution, Electrowinning & Smelting (Gold Room): Loaded carbon undergoes an acid wash to remove contaminants before being fed to a pressurized Zadra-style elution column. Here, a hot (130°C) caustic cyanide solution strips the gold from the carbon. The resulting pregnant solution is passed through electrowinning cells, where gold plates onto steel wool cathodes. The sludge from these cathodes, along with gravity concentrate from the ILR, is calcined and then smelted in an LPG-fired furnace with fluxes to produce the final product: gold doré bars. The stripped carbon is thermally regenerated in a kiln and returned to the CIL circuit.
Critical Data
The operational and design parameters for the Diamba Sud process plant are rooted in detailed testwork and engineering studies. The table below summarizes the key technical data that defines the circuit’s capacity, performance, and resource requirements.
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Design Throughput (Fresh Ore) | 250 | t/h | Nominal instantaneous feed rate (2.0 Mt/a) |
| Design Throughput (Oxide Blend) | 313 | t/h | For feed with ≥20% oxide (2.5 Mt/a) |
| SAG Mill Installed Power | 7.1 | MW | Variable speed drive, duty draw ~5.7 MW |
| Target Fresh Ore Grind Size (P80) | 106 | µm | Cyclone overflow product size |
| Target Oxide Ore Grind Size | ~75 | µm | Naturally finer, requires less grinding energy |
| CIL Leach Residence Time | 24 | hours | In 7 tanks at 45% solids density |
| Primary Crusher Capacity | 400 | t/h | At 70% availability on 24/7 schedule |
| Crushed Ore Stockpile Capacity | 19,000 | tonnes | Total capacity, ~3,000 t live capacity |
| Bond Work Index (BWi) – Fresh | 17.2 | kWh/t | Indicates medium hardness |
Additional Interesting Data and Summary
Beyond the core process stages, the Diamba Sud project design incorporates several noteworthy technical, environmental, and logistical elements that underscore its comprehensive planning. The plant will be powered by a dedicated on-site Heavy Fuel Oil (HFO) power plant, with electrical reticulation at 11kV and 415V across the site. A sophisticated Supervisory Control and Data Acquisition (SCADA) system, utilizing GE Fanuc RX3i PLCs and Citect SCADA software, will enable centralized monitoring and control from multiple locations, including the main CIL control room and crusher station, ensuring high levels of automation and operational efficiency.
Water management is a critical pillar of the project’s sustainability framework. The majority of process make-up water (70-85%) will be sourced from recycled supernatant water from the Tailings Storage Facility (TSF). Additional supply will come from a dedicated water storage dam filled by water harvesting, pit dewatering, and, as a contingency, abstraction from the Falémé River located 7 km east. Current modeling suggests river abstraction may not be necessary, highlighting a design focused on minimizing external water draw. The tailings and return water pipelines will be installed in a fully bunded and lined trench to mitigate environmental risk from potential leaks.
The reagent handling systems are designed for safety and efficiency. Cyanide is received in 1-tonne bulk bags, mixed into a 30% solution in a contained, bunded area, and dosed via a ring main. Lime, cyanide, caustic soda, hydrochloric acid, and flocculant storage are all sized to hold multiple days of supply, allowing for logistical flexibility, especially during Senegal’s wet season. The project anticipates significant reagent consumption differences between ore types, with lime use forecast at 10.5 kt/year for oxides versus only 0.7 kt/year for fresh ore.
Economically, the project is designed to transition smoothly through its mine life. The first year will process 1.78 million tonnes of oxide ore, leveraging its natural fineness and higher recovery potential. Years 2-4 will see a blended feed, gradually shifting to 100% fresh ore by Year 8. This phased approach allows the comminution circuit to be optimized for changing ore characteristics. With its robust, conventional flowsheet, strong water recycling ethos, and detailed execution planning, the Diamba Sud Gold Project is positioned as a technically sound and strategically important future producer for Fortuna Mining in West Africa’s burgeoning gold sector.
Source: Project: Diamba Sud Gold Project | Date: October 2025
Further Reading
- Exploration | Fortuna Mining Corp …
- Senegal’s Diamba Gold Project to Reach Construction …
- Fortuna Signals 2026 Go-Ahead for Building the Diamba …
Technical report and processing history
The following archived source profiles have been consolidated here to preserve the project’s processing history and study context.
Diamba Sud Gold Project — 2025 Technical Report
Diamba Sud Gold Project — 2025 Technical Report
| Company | MIQM |
| Date | 2025-10-15 |
| Region | Kédougou Region, Senegal |
| Commodities | Gold |
| Mine Type | Open Pit |
| Throughput | 2.0 Mt/a (fresh), 2.5 Mt/a (blend) |
| Mine Life | 8 years |
| Status | Development |
Executive Summary
This technical report outlines the proposed processing plant design for the Diamba Sud Gold Project located in the Kédougou Region of Senegal. The project involves an open-pit mine targeting gold mineralization, with a processing facility designed to handle both oxide and fresh mill feed materials. The plant is designed for a throughput of 2.0 Mt/a of fresh material or 2.5 Mt/a with a blend of at least 20% oxidized rock, operating at average head grades of 1.8 g/t Au for oxide and 1.6 g/t Au for fresh material.
The metallurgical testwork indicates the mineralization is free-milling with low sulfide lock-up, making it amenable to standard gold cyanidation treatment. The proposed flowsheet is robust and simple, comprising primary crushing, single-stage SAG milling, gravity recovery, and a Carbon-in-Leach (CIL) circuit. The design includes specific provisions for reagent management, water supply from harvesting dams and the Falémé River, and a SCADA-based control system to ensure operational efficiency and safety.
Operational parameters include a crushing circuit throughput of 400 t/h and a milling circuit designed for 250 t/h (fresh) or 313 t/h (oxide blend). The mine life schedule spans eight years, transitioning from oxide-dominated feed in the early years to fresh material later. The process plant design emphasizes reliability with duty/standby arrangements for critical equipment such as pumps and cyclones, and includes detailed tailings disposal and electrical reticulation plans.
Website: https://cdn.yahoofinance.com/prod/sec-filings/0001341335/000110465925116545/tm2532001d1_ex99-1.htm
Report Date: 2025-10-15
Region: Kédougou Region, Senegal
Project Status: Development
Commodity: Gold
Throughput: 2.0 Mt/a (fresh), 2.5 Mt/a (blend)
Mine Life: 8 years
Mine Type: Open Pit
Ore type:
Diamba Sud Process Design Balances Oxide Start, Fresh Ore Future
Fortuna Mining Corp. plans a single-stage SAG milling circuit with pebble crushing and a conventional CIL gold recovery train for its Diamba Sud project in Senegal. The plant is designed to treat a blend of oxide and fresh ore, with a layout that allows for a future SAG-ball mill conversion.
Opening Background
The Diamba Sud Gold Project, held by Fortuna Mining Corp. through its indirectly owned Senegalese subsidiary Boya S.A., is a proposed open pit gold mining operation in the Kédougou Region of Senegal, about 665 km southeast of Dakar and 83 km from the town of Kédougou. The project, which contains seven gold deposits in the northern DS1 block, is the subject of a feasibility study based on Mineral Resource and Mineral Reserve estimates with an effective date of April 10, 2026. Boya applied for an exploitation permit in February 2026. Its retention period for the exploration permit was extended 60 days to August 21, 2026, to allow filing of the feasibility study. Once an exploitation permit is granted, the State of Senegal will receive a 10% free carried interest in the new operating entity, with Fortuna holding the remaining 90%.
Critical Data
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Plant design throughput (fresh ore) | 2.0 | Mt/a | Design value |
| Plant design throughput (blend) | 2.5 | Mt/a | Based on blend of at least 63% fresh and 37% oxide ores |
| Average head grade (oxide) | 2.62 | g/t Au | Design value over LOM |
| Average head grade (fresh) | 1.48 | g/t Au | Design value over LOM |
| Crushing circuit throughput (oxide) | 381 | dry t/h | Design value at 75% dry plant utilization |
| Crushing circuit throughput (fresh) | 304 | dry t/h | Design value at 75% dry plant utilization |
| Milling circuit throughput (oxide) | 313 | dry t/h | Design value at 91.3% wet plant utilization |
| Milling circuit throughput (fresh) | 250 | dry t/h | Design value at 91.3% wet plant utilization |
| Grind size (P80) | 106 | µm | Design value for both oxide and fresh ore |
| CIL feed grade (oxide) | 2.62 | g/t Au | Design value |
| CIL feed grade (fresh) | 1.72 | g/t Au | Design value |
| Leach residence time | 24 | h | Total across pre-leach and leach tanks |
| Pre-leach residence time | 4 | h | In a single pre-leach tank |
| CIL slurry density | 45 | % solids | For fresh ore |
| SAG mill diameter | 8.53 | m | Design value |
| SAG mill effective grinding length | 5.93 | m | Design value |
| SAG mill installed power | 7.2 | MW | Design value |
| SAG mill pinion power draw | 2.3–5.7 | MW | Expected range |
| Bond Ball Mill Work Index (BWi) | 17.4 | kWh/t | Test result for fresh ore |
| Bond Crusher Work Index (CWi) | 7.3 | kWh/t | Test result for fresh ore |
| Bond Abrasion Index (Ai) | 0.222 | g | Test result for fresh ore |
| SMC breakage parameter (A*b) | 30.5 | Not applicable | Test result for fresh ore |
| Mineralization specific gravity | 2.74 | Not applicable | Test result for fresh ore |
| Reagent storage allowance | 42 | days | Minimum on-site bulk storage for all reagents |
Overview
The process plant at Diamba Sud is a conventional free-milling gold flowsheet built around crushing, SAG milling with pebble crushing, gravity recovery, and carbon in leach (CIL) with elution, electrowinning, and smelting. The design was developed from a metallurgical testwork program managed by Maca Interquip Mintrex and completed by ALS Metallurgy in Perth, supported by comminution circuit modelling by Orway Minerals Consultants.
Testwork showed the mineralization is free-milling with a low proportion of fine gold locked in sulfides, and the material is amenable to standard cyanidation. Comminution testing indicated the ore is moderate to hard, with some variability between oxide and fresh domains. The circuit selection process compared a single-stage SAG mill with pebble crushing against a SABC configuration, with the single-stage option chosen as the base case because of life-of-mine ore characteristics and operational flexibility. The plant layout includes space for a future ball mill that would allow conversion to a SABC circuit if needed.
Feed will come from open pit mines, blending oxide and fresh ore over the life of mine. The LOM schedule shows oxides as the dominant feed in Year 1, then fresh ore taking over from Year 2 onward.
Key Process Stages
Primary Crushing. Ore from the open pit is delivered by 100 t haul trucks to a ROM pad, where it is stockpiled by mineralization type and grade for blending. A front-end loader feeds a 130 m³ ROM bin, which discharges via an apron feeder into a single toggle jaw crusher rated at 185 kW. The crusher accepts nominal minus 800 mm rock, with a rock breaker handling oversize. Crushed product moves on a 1,500 mm wide conveyor to a surge bin with a live volume of approximately 103 m³, providing about 30 minutes of residence time. Excess material flows to a dead stockpile with a live capacity of roughly 7,500 dry tonnes, enough for approximately 24 hours of mill feed. Surge bin and reclaim feeders are controlled through a weightometer on the SAG mill feed conveyor.
Grinding and Classification. An 8.53 m diameter by 5.93 m long SAG mill performs primary grinding duty, with an installed power of 7.2 MW and a duty ball charge of 8–15%. The mill has a variable speed drive to adjust for changes in ore characteristics. During the initial oxide treatment period, the mill runs at about 50% of critical speed with a reduced ball charge of roughly 8.4%. As feed transitions to predominantly fresh ore, the mill speed increases to about 75% of critical speed with a ball charge around 10.1%. Mill discharge passes over a vibrating screen to separate pebbles, with undersize slurry reporting to a discharge hopper. Cyclone feed pumps in a duty/standby arrangement send slurry to a 20-pack classifying cyclone cluster with 13 operating cyclones. Cyclone overflow achieves a P80 of 106 µm and reports to the leaching circuit. A nominal 265% recirculating load is designed for oxide operation and 450% for fresh material.
Pebble Crushing. Oversize from the mill discharge screen reports to a 132 kW HP200 pebble crusher at a design rate of 144 dry t/h. The crusher operates at a closed side setting of 12 mm, with product returned to the SAG mill feed conveyor. A belt magnet and metal detector protect the crusher from tramp metal. If metal is detected, a flop gate bypasses the material back to the SAG mill.
Gravity Recovery. A portion of the cyclone underflow, from three cyclones, reports to a gravity scalping screen with a 2 mm aperture. Oversize from the screen returns to the SAG mill feed. Undersize feeds a single Knelson KC-QS40 centrifugal concentrator operating at a nominal feed rate of 225 t/h with a maximum of 250 t/h. The concentrator runs on a batch cycle of 30–40 minutes, producing a concentrate mass pull of roughly 50–65 kg per cycle. Concentrate goes to a Gekko ILR1000BA intensive leach reactor capable of treating up to 3,000 kg/day. Tailings from both the concentrator and reactor return to the mill discharge hopper for retreatment.
Trash Screening and Pre-Leach Thickening. Cyclone overflow passes over a trash screen, with oversize reporting to a trash bin. The slurry can bypass the thickener and go directly to leaching, typically during oxide treatment, or pass through a leach feed thickener to achieve the required solids concentration during fresh ore operations. Thickener overflow reports to the process water tank for reuse, and underflow is pumped to a distribution box feeding either the first or second CIL tank.
Carbon in Leach Circuit. The CIL train consists of seven tanks of nominal 1,920 m³ each, providing a total slurry residence time of 24 hours at 45% solids by weight for fresh ore. All tanks have hollow shaft agitators for air injection to satisfy oxygen requirements. Carbon is held in all tanks except the first, where the inter-stage screen acts as a safety screen. Recessed impeller carbon transfer pumps advance carbon between tanks. Loaded carbon from tank 2 undergoes an acid wash before elution. A vibrating carbon safety screen adjacent to tank 6 collects any escaping carbon for manual reintroduction.
Elution, Electrowinning and Smelting. The elution circuit is a split AARL system with a strip capacity of 6 t per cycle, using two columns: an acid wash column and an elution column. The strip solution, prepared with sodium hydroxide and sodium cyanide, is preheated to about 95 °C and then to an operating range of 125–140 °C. The elution sequence uses one bed volume of strip solution, four bed volumes of hot elution, two bed volumes of rinse water, and two bed volumes of cooldown water. Total acid wash time is about three hours, and the elution cycle about nine hours. Pregnant solution circulates through electrowinning cells for 8–12 hours. Barren carbon transfers to a dewatering screen before a regeneration kiln operating at a nominal feed rate of 300 kg/h over a 20-hour period per day. Gold sludge from both the gravity and elution circuits is calcined and smelted in a diesel-fired furnace to produce doré bars, with gravity and CIL sludges refined separately for metallurgical accounting.
Tailings Disposal. Tailings are pumped to a tailings storage facility through an above ground pipeline, except where buried at road crossings. The pipeline is laid in a fully bunded and lined trench. Leaks are detected by comparing readings from two flow meters, one at the plant and one at the TSF.
Additional Interesting Data and Summary
The process design carries a few notable elements worth flagging. The surge bin and dead stockpile arrangement means the mill can keep running through crusher downtime, with the stockpile holding roughly 24 hours of feed. Lime is added directly to the mill feed conveyor to raise slurry pH for cyanidation, and quicklime consumption is estimated at about 3.3 kt per year for oxide and 0.5 kt for fresh mineralization.
Power for the process plant comes from a planned site-based heavy fuel oil power plant, with distribution at 11 kV and 415 V. The water supply strategy draws 70–92% of process make-up water from recycled water from the TSF supernatant pond, supplemented by a water harvesting facility, groundwater, and open pit dewatering.
The qualified person for the report observed that the flowsheet is conventional and well-established for free-milling gold, and no significant technical risks were identified with the selected process design. Testwork coverage for certain deposits, including Southern Arc and Moungoundi, is comparatively limited, but the available results were considered sufficient to support the selected flowsheet and recovery assumptions.
Key Processes
- Conventional free-milling gold processing route with crushing, SAG milling, gravity recovery, CIL, and gold recovery via elution, electrowinning, and smelting.
- Single-stage SAG milling circuit with pebble crushing as the base case, with layout provision for future conversion to a SABC configuration.
- Gravity recovery circuit treating 24–32% of cyclone underflow, with intensive leach of concentrate.
- Flexible CIL operation with one pre-leach tank and six leach tanks, providing approximately 24 hours of total residence time.
- Pre-leach thickening for fresh ore operations.
Source: Diamba Sud Gold Project Technical Report, July 13, 2026. Project website: Diamba Sud Gold Project
