Fortuna delivers robust PEA for Diamba Sud Gold Project in Senegal: After-tax IRR of 72% and NPV5% of US$563 million using US$2,750 per ounce (All financial information contained herein are expressed in US dollars
NEWS RELEASE
Fortuna delivers robust PEA for Diamba Sud Gold Project in
Senegal: After-tax IRR of 72% and NPV5% of US$563 million using
US$2,750 per ounce
(All financial information contained herein are expressed in US dollars unless otherwise stated)
Vancouver, October 15, 2025: Fortuna Mining Corp. (NYSE: FSM | TSX: FVI) is pleased
to report the results of the Preliminary Economic Assessment (PEA) prepared for the Diamba Sud
Gold Project in Senegal.
The PEA supports robust project economics for the development of an open-pit mine and conventional
carbon-in-leach (CIL) processing plant. At a gold price of $2,750 per ounce, t he assessment unveils
an after-tax NPV5% of $563 million, an IRR of 72 percent, and a payback period of ten months. During
the first three years of production, Diamba Sud is projected to deliver an average of 147,000 ounces
of gold per year at an All-In Sustaining Cost1 (AISC) of $904 per ounce.
Construction capital cost is estimated at approximately $283.2 million. Project funding is derisked by
the strength of Fortuna’s balance sheet and robust cash flow generation. As of the end of the second
quarter of 2025, Fortuna reported liquidity of $537.3 million and a net cash position of $214.8 million.
Jorge A. Ganoza, President and CEO at Fortuna, commented, “The PEA highlights the strong value
Diamba Sud brings to Fortuna ’s portfolio , using a long-term gold price of $2,750 per ounce . With
permitting and the Definitive Feasibility Study underway, we expect to make a construction decision in
the first half of 2026. ” Mr. Ganoza continued, “ Ongoing exploration is advancing with five drill rigs
focused on expanding open areas of mineralization and to upgrade the small portion of Inferred Mineral
Resources to the Measured and Indicated categories by year -end. With continued exploration
success, w e expect to enhance Diamba Sud’s life of mine production profile beyond a decade .”
Mr. Ganoza concluded, “ Additionally, we have approved a $17 million budget to advance early
construction works, including the expansion of camp and ancillary facilities, as well as detailed
engineering activities.”
Note:
1. This is a non -GAAP financial measure. The definition and purpose of this non -GAAP financial measure is included under the heading
“Cautionary Note on Non-GAAP Measures” in this news release.
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PEA Key Highlights
Table 1 summarizes the key assumptions, operational parameters, economic results, and AISC values
from the PEA.
Table 1: PEA key highlights
Metrics Units Results
Gold price $/oz 2,750
Life of mine year 8.1
Total mineralized material mined1 Mt 17.75
Contained gold in mined resource1 koz 932
Strip ratio w:o 5.5:1
Throughput initial 3 years (oxide) Mtpa 2.5
Throughput @ nameplate (fresh) Mtpa 2.0
Head grade g/t Au 1.63
Recoveries % 90%
Gold production
Total Production over LOM koz 840
Average annual production, LOM koz 106
Average annual production, first 3 years koz 147
Per unit costs over LOM
Total mining costs $/t, mined $4.82
Processing $/t, processed $13.91
G&A $/t, processed $6.70
Cash costs1
Average operating cash costs2, LOM $/oz $1,081
Average operating cash costs2, first 3 years $/oz $759
AISC1
Average AISC2, LOM $/oz $1,238
Average AISC2, first 3 years $/oz $904
Capital costs
Initial capital expenditure $ M $283
Sustaining capital, operations + Infrastructure (includes closure costs) $ M $48
NPV5%, pre-tax (100% project basis) $M $772
Pre-tax IRR % 86%
NPV5%, after-tax (100% project basis) $M $563
After-tax IRR % 72%
Payback period year 0.8
Annual EBITDA 2
Average EBITDA2 over LOM $ M $167
Average EBITDA2 over first 3 years $ M $277
Notes:
1. The pit optimization shells used for the mining inventory were generated using a gold price of $2,300 per ounce.
2. This is a non -GAAP financial measure. The definition and purpose of this non -GAAP financial measure is included under the heading
“Cautionary Note on Non -GAAP Measures” in this news release. Non -GAAP financial measures have no standardized meaning under
IFRS and therefore, may not be comparable to similar measures presented by other issuers.
3. Average operating cash costs and average AISC represent costs for projected production for the LOM at the time of gold sales.
4. The PEA is presented on a 100 percent project basis. However, upon the granting of the exploitation permit, the Senegalese Government
will be entitled to a 10 percent free-carried interest in the Project, with the right for the State to acquire an additional contributory interest
of up to 25 percent.
5. The economic analysis was carried out using a discounted cash flow approach on a pre -tax and after-tax basis, based on the gold price
of $2,750/oz.
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6. The IRR on total investment that is presented in the economic analysis was calculated assuming a 100% ownership in Diamba Sud.
7. The NPV was calculated from the after -tax cash flow generated by the Project, based on a discounted rate of 5% and a n effective date
of October 10, 2025.
8. The PEA assumes that the percentage of certain royalties and taxes payable to the State, the percentage of the investment tax credit
available to the company and the percentage payable to the social development fund will be in accordance with the provision s of the
Mining Convention between Boya S.A. and the State of Senegal dated April 8, 2015. There can be no assurance that such provisions
will not be renegotiated by the State as part of the exploitation permit approval process.
9. The PEA is preliminary in nature, and 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, as such, th ere is no
certainty that the PEA results will be realized.
Exploration Upside: Resource Delineation and Exploration Drilling
Opportunities exist to further strengthen and enhance Diamba Sud ’s economic foundation through
continued drilling, resource extension testing, and definition of new targets. Successful exploration
programs are expected to extend the Life of Mine (LOM) gold production profile to beyond a decade.
Exploration d rilling completed since the data cut -off for the Mineral Resource estimate in the PEA
comprises 125 drill holes totaling 1 5,794 meters. Results from this recent drilling include drill hole
DSDD488 that intersected 22.7 g/t Au over an estimated true width of 21.6 meters , highlighting
substantial exploration upside (refer to Fortuna news release dated August 13, 2025: “ Fortuna drills
22.7 g/t gold over 21.6 meters at Southern Arc, Diamba Sud Gold Project, Senegal ”).
Exploration programs for the second half of 2025 are focused on:
• Infill drilling at Area A, Area D, Karakara, Moungoundi, and Southern Arc to convert Inferred
Resources to Indicated Resources in support of the forthcoming Definitive Feasibility Study
(DFS) and Mineral Reserve estimate.
• Step-out and resource expansion drilling at Southern Arc aimed at increasing the Mineral
Resource and enhancing the LOM gold-production profile from year four onward.
• Testing prospective targets identified across the broader Diamba Sud tenement package,
which offer additional growth potential.
• Continuing exploration at Fortuna’s Bondala properties , adjacent to Diamba Sud , where
geophysical surveys and auger drilling have identified anomalies to be follow ed up with
targeted drill programs.
Diamba Sud PEA Overview
The PEA outlines the design of an open pit gold mining operation targeting a series of deposits
including Area A, Area D, Karakara, Western Splay, Kassassoko, Moungoundi , and Southern Arc
which will feed a central gold processing facility over the current 8.1 -year LOM. The assessment is
based on Diamba Sud´s Mineral Resource estimate, which comprises an Indicated Mineral Resource
of 14.2 million tonnes (Mt) at an average gold grade of 1.59 grams per ton ne (g/t), containing
724,000 ounces of gold, and an Inferred Mineral Resource of 6.2 Mt at an average grade of 1.44 g/t
gold, containing 285,000 ounces of gold, reported as of July 7, 2025 ( refer to Fortuna news release
dated August 5, 2025, “Fortuna Advances Diamba Sud Gold Project in Senegal with Updated Mineral
Resources; PEA Completion Targeted for Q4 2025”).
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Mining and Processing
The PEA and mine plan outline the design of an open pit gold mining operation feeding a central gold
processing facility over the 8.1-year LOM. The assessment anticipates the concurrent development of
multiple deposits, including Area A, Area D, Karakara, Western Splay, Kassassoko, Moungoundi, and
Southern Arc, with no more than three pits mined at any one time (refer to Figure 1).
The production strategy targets an initial throughput of 2.5 million tonnes per annum (Mtpa) during the
first three years of operation, supported by the high oxide content at Area D, before transitioning to a
sustained rate of 2.0 Mtpa from year four onward as the feed becomes predominantly fresh material.
Exploration drilling completed at the Southern Arc deposit subsequent to the Mineral Resource
estimate in the PEA has intersected near-surface mineralization to the south and east of the currently
defined pit limits. It is anticipated that these results will be incorporated in future evaluations to enhance
gold production in the later years of the LOM.
The pit optimization shells used to define the mining inventory were generated using a gold price of
$2,300 per ounce and a revenue factor of 1.0. Optimization parameters incorporated government
royalties, refining, mining, processing, and general and administrative costs to ensure realistic pit
designs and economic assumptions.
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Figure 1: Diamba Sud PEA Production Profile: Annual gold production profile over the projected LOM, highlighting
the contribution from individual deposits and the transition from oxide to fresh material.
Mining activities at Diamba Sud will employ conventional open pit methods. Drilling and blasting are
planned for both oxide and fresh mineralized material, followed by conventional truck -and-shovel
operations for the movement of potentially mineralized material and waste within the pits.
The Diamba Sud process plant design is based on a metallurgical flowsheet developed to produce
gold doré at optimum recovery while minimizing initial capital and operating costs. The flowsheet
comprises conventional crushing, milling (single-stage semi-autogenous grinding mill in closed circuit
with cyclones), gravity recovery, carbon-in-leach processing, carbon elution, and gold recovery.
A summary of the key operating and production statistics from the PEA is presented in Table 2.
0
20
40
60
80
100
120
140
160
180
200
220
240
Year 0 Year 1 Year 2 Year 3 Year 4 Year 5 Year 6 Year 7 Year 8
Gold Mined (koz)
Life of Mine
Area A
Area D
Karakara
Kassasoko
Moungoundi
Southern Arc
Western Splay
Gold Production
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Table 2: Diamba Sud LOM Mining and Processing Plan Metrics
Unit Year -1 Year 0 Year 1 Year 2 Year 3 Year 4 Year 5 Year 6 Year 7 Year 8 LOM
Area A
Potentially mineralized
material mined kt 9 122 923 2,044 3,098
Au grade g/t 1.17 0.97 1.84 1.45 1.54
Area D
Potentially mineralized
material mined kt 69 1,870 1,718 1,666 5,323
Au grade g/t 0.87 2.51 1.33 1.41 1.76
Karakara
Potentially mineralized
material mined kt 21 974 1,745 2,741
Au grade g/t 1.97 1.87 1.83 1.84
Kassassoko
Potentially mineralized
material mined kt - 30 1,099 1,130
Au grade g/t - 1.04 0.97 0.97
Moungoundi 34.3
Potentially mineralized
material mined kt 499 296 795
Au grade g/t 0.95 1.28 1.07
Southern Arc 15.2
Potentially mineralized
material mined kt 0 1,532 1,008 299 264 3,103
Au grade g/t 0.47 1.58 1.68 1.65 1.98 1.65
Western Splay 16.8
Potentially mineralized
material mined kt 121 1,172 270 1,564
Au grade g/t 1.12 1.45 3.22 1.73
Total
Potentially mineralized
material mined kt 90 2,845 3,585 2,847 1,925 1,931 2,373 1,862 296 17,754
Au grade g/t 1.13 2.29 1.56 1.43 1.77 1.76 1.47 1.11 1.28 1.63
Contained gold koz 3.3 209.4 180.3 130.5 109.6 109.0 111.9 66.3 12.2 932.4
Waste mined kt 2,322 16,326 15,588 16,380 17,166 13,793 7,264 7,597 656 97,092
Total mined kt 2,412 19,171 19,173 19,228 19,091 15,723 9,637 9,459 953 114,846
Stockpile
Start of period kt 90 580 1,665 2,013 1,712 1,532 1,875 1,524 n/a
Grade g/t 1.13 0.76 0.57 0.59 0.68 0.59 0.59 0.58 n/a
Processing
Material milled kt 2,354 2,500 2,500 2,225 2,111 2,030 2,213 1,821 17,754
Head grade g/t 2.62 2.04 1.53 1.55 1.72 1.62 1.03 0.70 1.63
Contained gold koz 198.5 163.8 122.7 110.8 117.0 105.7 73.2 40.7 932.4
Recovery % 92.5 92.1 86.1 88.2 90.0 91.9 87.9 86.6 90.1
Gold production koz 183.7 150.9 105.6 97.7 105.3 97.2 64.3 35.3 840
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Tailings, Water and Power
The tailings management system will comprise a tailings pipeline and a water return pipeline housed
within a geomembrane -lined trench , with associated tailings pumps. The Tailings Storage Facility
(TSF) will be fully lined with a geomembrane and will be developed as a side-valley storage facility
formed by robust , multi-zoned earth -fill embankments . It is designed to accommodate 17.8 Mt of
tailings and will be constructed using the downstream methodology, in accordance with industry best
practices and the Global Industry Standard on Tailings Management (GISTM).
A water storage dam will serve as the main collection and storage facility for clean, raw, and process
water. Raw water is currently assumed to be supplied via a pipeline from the Falémé River ,
supplemented by pit dewatering activities . Ongoing studies are evaluating the potential to develop a
water harvesting facility as an alternative source. Process water from the TSF will be recycled back to
the plant, with site operations designed as a closed -circuit system to maximize water reuse and
minimize environmental impacts on surrounding communities.
Power for Diamba Sud is expected to be self -supplied through an on -site power plant. The current
plan envisages a heavy fuel oil power plant constructed in an N+1 configuration, supported by light
fuel oil generators to meet site -wide demand. In parallel, a hybrid solar photovoltaic system is being
evaluated as part of the preparation of the DFS.
Capital Costs Summary
The PEA estimates the total initial capital required to develop Diamba Sud to be $283.2 million ,
including $4 .0 million in capitalized closure costs to be deposited into escrow and a $46.4 million
contingency. Sustaining capital is estimated at an additional $40 .0 million, directly related to mining
operations, processing, and infrastructure sustaining capital, along with a further $8.0 million in closure
costs over the 8.1-year LOM.
Mining pre -production capital includes all mining activities required prior to commissioning of the
processing facility. A total of 2.3 Mt of waste and 90 kt of potentially mineralized material will be mined
to establish a stockpile ahead of processing operations. All contractor mobilization and setup costs are
included in the pre-production capital allowance.
The processing plant capital estimate relates to a facility with a nameplate throughput of 2.0 Mtpa,
designed to accommodate up to 2.5 Mtpa. The capital cost estimate is based on an Engineering,
Procurement, Construction, and Management (EPCM) implementation approach.
A summary of estimated capital costs is presented in Table 3, and the estimated annual sustaining
capital costs are set out in Table 4.
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Table 3: Summary of Initial Development Capital Costs
Capital Costs Value ($ M)
Construction costs $191.7
Pre-production costs (excluding mining) $21.6
Mining pre-stripping $19
Contingency $46.4
Withholding taxes, duties, levies $4.5
Total $283.2
Table 4: Estimated Annual Sustaining Capital Costs
Year Units
Year Year Year Year Year Year Year Year Year Year
Total
1 2 3 4 5 6 7 8 9 10
TSF lifts $ M 4.5 - 7.3 - 11.7 - 11.1 - 34.6
Roads $ M - 2.1 0.2 - - 0.1 0.3 - 2.7
Surface water
management $ M - 1.0 0.9 - - - 0.3 - 2.3
Closure $ M - - 0.6 0.6 0.6 0.6 0.6 5.3 8.5
Total $ M 4.5 3.1 9.1 0.6 12.3 0.7 12.4 5.3 48.0