Name of the Project
Diamba Sud gold project.

Location
The Kédougou region, south-east Senegal.

Project Owner/s
Diamba Sud is operated by Boya SA, a wholly owned indirect subsidiary of Fortuna Mining Corp. 

Project Description
Fortuna released the feasibility study on June 29, 2026. The study supersedes the October 2025 preliminary economic assessment and provides a higher-confidence development basis.

The feasibility study outlines a conventional openpit gold operation comprising the Area A and Area D deposits, which will be mined as one contiguous pit, as well as the Karakara, Kassassoko, Moungoundi, Southern Arc and Western Splay deposits. 

Mining will use drilling and blasting followed by truck-and-shovel methods. The mine plan provides for 20.5-million tonnes of ore grading 1.75 g/t gold containing 1.151-million ounces, and about 130-million tonnes of waste, resulting in a life-of-mine (LoM) strip ratio of 6.3:1.

Ore will be treated in a conventional carbon-in-leach plant producing gold doré. The flowsheet comprises crushing, single-stage semiautogenous grinding in closed circuit with cyclones, gravity recovery, carbon-in-leach processing, carbon elution and gold recovery. 

The plant is designed for two-million tonnes a year of fresh ore and up to 2.5-million tonnes a year with an oxide blend, averaging about 2.26-million tonnes a year over the LoM.

The project is expected to produce 1.053-million ounces of gold over 9.4 years at an average metallurgical recovery of 91%. Average production is forecast at 158 000 oz/y during the first four years and 116 000 oz/y over the LoM. 

Supporting infrastructure will include a fully geomembrane-lined, downstream-raised tailings storage facility designed for 20.5-million tonnes of tailings; a water storage dam and water harvesting dam; process-water return systems; access and internal roads; administration, security, medical, laboratory and services buildings; and a 329-person accommodation camp. Water will be managed as a closed-circuit system to maximise recycling. Power is planned to be supplied using a hybrid system combining heavy-fuel-oil generation, solar photovoltaic capacity and battery energy storage, with solar integration targeted during the first year of operations.

Mineral resources, exclusive of the mineral reserve, comprise 3.364-million tonnes of indicated material grading 1.12 g/t gold for 121 000 oz and 1.632-million tonnes of inferred material grading 1.30 g/t gold for 68 000 oz. The deposits remain open to further growth, particularly at Southern Arc, and continued drilling is intended to test extensions and convert additional resources to reserves.

Potential Job Creation
None stated.

Net Present Value/Internal Rate of Return
At the feasibility study base-case gold price of $3 500/oz, the project has an after-tax net present value (NPV), at a 5% discount rate, of $1.009-billion and an internal rate of return (IRR) of 60%, with a payback of about 12 months. The corresponding pretax NPV and IRR are estimated at $1.379-billion and 70% respectively. At $4 000/oz, the after-tax NPV increases to $1.287-billion and the IRR to 72%, with an 11-month payback. 

Capital Expenditure
Initial development capital is estimated at $397.5-million.

Planned Start/End Date
A final investment decision is expected after receipt of the exploitation permit. Subject to a positive decision and the remaining approvals, full construction could start in the fourth quarter of 2026 following the wet season. Structural-steel erection and mechanical installation are planned during 2027, followed by practical completion and commissioning in 2028. First gold is targeted in mid-2028.

Latest Developments
Fortuna has approved a $73-million early-works programme, of which about $18-million had been spent by June 29, 2026. 

During the second quarter, the project advanced towards a final investment decision following receipt of the environmental- and social-impact assessment and publication of the feasibility study results. The related NI 43-101 technical report is expected to be filed on SEDAR+ within the required 45-day period. 

Work under way includes construction of the new site access road, as well as the installation of additional temporary accommodation and office facilities for the owner's project and preproduction teams. The contract for a new 320-person camp has been awarded while tendering for other major construction packages is well advanced. 

Letters of award have been issued for critical-path contracts, including the process plant and power station, consequently securing the delivery schedule for the heavy-fuel-oil generators, which are expected in mid-2027. Tenders have also been launched for all process plant long-lead equipment, including the semiautogenous grinding mill and jaw crusher, with purchase orders expected early in the third quarter of 2026. The project remains positioned for a final investment decision.

Exploration drilling is continuing to test open extensions, upgrade inferred resources and assess further reserve conversion. Additional optimisation will focus on detailed engineering, mine sequencing, procurement and operating-cost refinement as the project advances towards construction.

Key Contracts, Suppliers and Consultants
Fortuna with support from independent specialists Lycopodium, Knight Piesold, Kenmore Mine Consulting, SOJUFISC, Infinity Corporate Finance, Piteau Associates, Entech and Earth Systems (feasibility study); African Power Services (letter of intent – engineering, procurement and construction contractor for the power station, and securing the heavy- and light-fuel-oil generators). 

Contact Details for Project Information
Fortuna Mining Corp, tel +1 604 484 4085 or email info@fmcmail.com.