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 UNDER THE SECURITIES EXCHANGE ACT OF 1934

For the month of November 2025

Commission File Number 001-35297

Fortuna Mining Corp.

(Translation of registrant’s name into English)

1111 Melville Street, Suite 820, Vancouver, British Columbia, Canada V6E 3V6

(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  ¨                                 FORM 40-F  x

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.

Exhibits:

Exhibit 99.1

Diamba Sud Gold Project,

Kédougou Region, Senegal

Technical Report,

Effective Date: October 15, 2025

Prepared for Fortuna Mining Corp.

Suite 820, 1111 Melville Street, Vancouver, BC, V6E 3V6. Tel: (604) 484 4085

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

Forward- Looking Statements

This Technical Report contains certain forward-looking information and forward-looking statements within the meaning of applicable securities legislation and may include future-oriented financial information (collectively, “Forward-looking Information”). Forward-looking Information in this Technical Report includes, but is not limited to, statements regarding: the Company’s plans and expectations for the Diamba Sud Project, including the estimattion of mineral resources the estimation of future mineral resources at the project; the Company’s ability to convert existing mineral resources into categories of higher geological confidence or mineral reserves; the projected yearly gold production profile, all-in sustaining costs (“AISC”), mill throughput and average grades; future plans for exploration drilling; the projected economics of the project, including total gold sales, margins, taxes, average annual production, the net present value of the project, the internal rate of return on the project, project payback period, average yearly free cash flow, life of mine unit costs, projected mine life, the total initial capital and sustaining capital required; estimated operating costs; the project design, including the location of the tailings management facility, process plant, water storage dam, infrastructure area, stockpile areas, camp; and the proposed open pit mine plans; the plans for completing the early works program; the project development timeline to production including the Company’s work relating to its environmental impact assessment statement and obtaining the permit, the permitting of future phases of the project, the timing of the completion of future studies including a feasibility study, obtaining an exploitation permit for the project, other permitting approvals including an environmental permit, and the development and construction of a mine and production at the project, including the constructing of a series of open pit mines; the timing of and future prospects for exploration and any expansion of the project, including upside associated with the project and the Company’s adjacent permits; the potential for expanding the initial mineral resource and the potential for identifying additional mineralization in areas of intercepts and conceptual areas for extension and expansion; potential recovery rates or processing techniques; the potential for a hybrid solar power plant; ongoing studies to optimize the mine design and enhance operational efficiency; the possibility of reducing capital and operating costs through engineering and optimization studies; potential to enhance socio-economic impacts of the Project; and opportunities to reduce the impact of the operations on the environment.

Often, but not always, these forward-looking statements can be identified by the use of words such as “anticipates”, “believes”, “plans”, “estimates”, “expects”, “forecasts”, “scheduled”, “targets”, “possible”, “strategy”, “potential”, “intends”, “advance”, “goal”, “objective”, “projects”, “budget”, “calculates” or statements that events, “will”, “may”, “shall”, “could”, “should” or “would” occur or be achieved and similar expressions, including negative variations.

The material factors or assumptions regarding Forward-looking Information contained in this Technical Report are discussed in this report, where applicable. Forward-looking Information is subject to known and unknown risks, uncertainties and other factors that may cause actual results and developments to differ materially from those expressed or implied by such Forward-looking Information. Relevant risks and other factors include,

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

without limitation: the estimation of Mineral Resources, the realization of resource estimates and mine plan, any potential upgrades of existing resource estimates, gold metal prices, the timing and amount of future exploration and development expenditures, the estimation of initial and sustaining capital requirements, the estimation of labour and operating costs; fluctuations in foreign exchange or interest rates; the possibility of material increases in costs and inflation and effects of same on the supply chain which could impact capital and operating costs; extended procurement and delivery times for key mechanical and power generation equipment may lead to delays; the ability to obtain qualified staff the availability of necessary financing and materials to continue to explore and develop the Company’s properties in the short and long-term, the progress of exploration and development activities; dependence of operations on construction and maintenance of infrastructure; the receipt of necessary regulatory approvals, the Company’s ability to maintain existing or obtain all necessary permits, licenses and regulatory approvals, including an exploitation permit and environmental permit, in a timely manner or at all; changes in laws, regulations and government practices, including environmental, tax, export and import laws and regulations; that the evolution of local content laws in Senegal which may affect contracting and recruitment; legal restrictions relating to mining; that the percentage of the taxes, royalties payable to the State and the contributions to the community development fund are consistent with the provisions of Boya’s Mining Convention; the viability, economically and otherwise of developing the Diamba Sud Project; economic and politicial risks associated with operating in foreign countries, including emerging country risks, exchange controls, and corruption; political developments in Senegal being consistent with Fortuna’s expectations; and risks relating to expropriation; increased competition in the mining industry and assumptions with respect to currency fluctuations, environmental risks including risks related to climate change; risks related to artisanal mining on the Project title disputes or claims, and other similar matters; the risk that the State of Senegal may elect to purchase up to an additional 25% interest in Boya SA at a “fair price” determined through an independent valuation upon the granting of the exploitation permit as is permissible under Senegalese mining legislation; uncertainties and hazards associated with gold exploration, development and mining, including but not limited to environmental hazards, accidents, operational stoppages, and other factors as described in the section 'Risk Factors' in Fortuna’s current Annual Information Form for the year ended December 31, 2024. Readers are cautioned that the foregoing factors are not exhaustive. Although the Company has attempted to identify important factors that could cause actual actions, events, or results to differ materially from those described in these Forward-looking Statements, there may be other factors that cause actions, events or results to differ from those anticipated, estimated or intended.

Forward-looking Information is designed to help readers understand views as of that time with respect to future events and speaks only as of the date it is made. All the Forward-looking Information in this Technical Report is qualified by these cautionary statements. Except as required by applicable law, Fortuna and the Qualified Persons who authored this Technical Report assume no obligation to update publicly or otherwise revise any

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

Forward-looking Information in this Technical Report, whether because of new information or future events or otherwise.

Cautionary Note to United States Investors Concerning Estimates of Reserves and Resources

The Company is a Canadian “foreign private issuer” as defined in Rule 3b-4 under the Exchange Act and is permitted to prepare the technical information contained herein in accordance with the requirements of the securities laws in effect in Canada, which differ from the requirements of the securities laws currently in effect in the United States.

Technical disclosure regarding the Diamba Sud Project included in this Technical Report was prepared in accordance with National Instrument 43-101 — Standards of Disclosure for Mineral Projects (“NI 43-101”). NI 43-101 is a rule developed by the Canadian Securities Administrators that establishes standards for all public disclosure an issuer makes of scientific and technical information concerning mineral projects. NI 43-101 differs significantly from the disclosure requirements of the Securities and Exchange Commission (the “SEC”) generally applicable to U.S. companies. Accordingly, information contained herein is not comparable to similar information made public by U.S. companies reporting pursuant to SEC disclosure requirements.

Cautionary Note Regarding Non-IFRS Measures

This Technical Report includes certain terms or performance measures and ratios commonly used in the mining industry that are not defined under International Financial Reporting Standards (“IFRS”), including earnings before interest, tax, depreciation and amortization (“EBITDA”), cash costs and AISC per payable ounce of gold sold. Non-IFRS measures do not have any standardized meaning prescribed under IFRS and, therefore, they may not be comparable to similar measures employed by other companies. Accordingly, these measures are intended to provide additional information and should not be considered in isolation or as a substitute for measures of performance prepared in accordance with IFRS.

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

Contents

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

Tables

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

Figures

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

This Technical Report (the Report) was prepared by Mr. Eric Chapman, P.Geo., Mr. Paul Weedon, MAIG, Mr. Raul Espinoza, FAusIMM (CP), Mr. Mathieu Veillette, P.Eng., and Dr. Leendert (Leon) Lorenzen, FAusIMM (CP) for Fortuna Mining Corp. (Fortuna) on the Diamba Sud Project (the Project) located in the Kédougou Region of Senegal.

The Diamba Sud Project is operated by Boya S.A. (Boya), a 100% indirectly owned Fortuna subsidiary. The Government of Senegal will assume a 10% free carried ownership interest in Boya when an exploitation permit is granted.

The Report discloses Mineral Resource estimates for the Project and a Preliminary Economic Assessment (PEA) based on those estimates.

Costs are in US dollars (US$) unless otherwise indicated.

The Diamba Sud Project is located within the Department of Saraya in the Kédougou Region and within the Arrondissement of Bembou. It is situated approximately 50 km north of the Senegal-Guinea border, and is approximately 7 km to the west of the Falémé River which, in this region, defines the international border between Senegal and Mali. The Project is approximately 665 km southeast of the Senegalese capital Dakar and 83 km northeast from the nearest town, Kédougou.

The Project comprises two blocks: DS1 and DS2 linked by a narrow strip of some 25 m width in order for the two blocks to be classed as contiguous and one permit area. DS1 is centered upon co-ordinates 11° 28’ 23.17” W and 12° 55’ 46.55” N. DS2, the southern block some 20 km to the south is centered upon co-ordinates 11° 26’ 2.68” W and 12° 45’ 13.61” N.

Elevations range between 100 m and 380 m above mean sea level. The region features low to moderate relief, consisting of broad lateritic plateaus, eroded valleys, and gentle slopes.

The landscape primarily comprises forested savanna with patches of grassland and forest. Notable flora include Baobab (Adansonia digitata), Madd (Saba senegalensis), Jujube (Ziziphus mauritania), and the Locust Bean Tree (Parkia biglobosa). Larger trees are often localized along river channels where seasonal rivers flow and the lateritic plateau has eroded, while vegetation in the area is predominantly grasses and small shrubs, characteristic of the climate.

From Dakar the Project site is accessed via the all-weather paved N1 highway southeast to the city of Tambacounda, the regional center of Senegal. From Tambacounda, the N7 can be taken southeast to Kédougou where it joins the Kédougou–Saraya road which connects Kédougou to the village of Saraya. From Saraya the paved N24 road is frequented by trucks taking goods to and from Mali, passes through the Diamba Sud permit area, and continues through to the Senegal-Mali border. Due to frequent use by trucks carrying heavy loads, road conditions can be locally very poor. However, in almost all cases the main roads remain open to vehicles throughout the year. Access throughout the permit area is taken via a combination of paved and laterite roads and dirt tracks.

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

Access by air is possible via an asphalt airfield in Kédougou. The Government has announced numerous plans to transform the airport into an international airport with regular scheduled flights, but development of the airport is yet to take place. Thus, the only currently available options for flights are two charter companies that operate from Dakar with flights taking approximately 2–3 hours.

The Diamba Sud permit is an exploration permit (permis de recherche) which was granted to Boya in June 2015 under the 2003 Mining Code before the 2016 Mining Code came into effect, and therefore it remains subject to the 2003 Mining Code for its duration and validity. The exploration permit was granted for an initial period of three years, subject to being renewed twice for additional periods of three years. It was last renewed on June 9, 2021, for a period of three years, being the second and final renewal and which expired on June 9, 2024. However, Fortuna obtained a special two-year retention period to complete the works necessary for a PEA, and to conduct the environmental studies that are required in support of an application for a mining license. This retention period is valid until June 21, 2026, and requires the submission of a request for an exploitation permit before this date and at least four months before the expiry of the exploration permit.

The permit comprises two blocks, the northern block, DS1 is approximately 46.56 km² and the southern block, DS2, some 20 km to the south is approximately 6.31 km², for a total permit area of 53.46 km² (including the corridor of land connecting the two parcels.

Mineral exploration permits, within their boundaries, entitle the holder within the boundaries of its perimeter, on surface and indefinitely in depth, the exclusive rights to explore for the nominated mineral commodities specified (in this case, gold), as well as encumbrance-free disposal of materials extracted during the exploration process. Such permits allow for beneficial ownership to be held by a foreign entity, such as Fortuna, through Boya, its wholly-owned Senegalese subsidiary.

Boya has full and unrestricted surface rights to the land covered by the exploration permit. The perimeter of the exploration permit is free to access and is not subject to any kind of restriction, subject to the applicable mining regulation.

The Diamba Sud Project is not subject to any back-in rights, liens, payments or encumbrances.

There are royalties attached to the mineral concessions; however, the only royalties that affect the Mineral Reserves and have been considered in the economic analysis are:

Prior to 1993 there is no known or recorded systematic mineral exploration carried out on the property, although regionally the area was surveyed by the Bureau de Recherches Géologiques et Minières (BRGM) as part of the Senegal Plan minerale in 1983. The first

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

recorded exploration activities were carried out by Anmercosa Exploration (a subsidiary of Anglo American plc) from 1993 to 1996, as part of a joint venture agreement with Iamgold Corporation (Iamgold). This work was carried out over the larger Bambadji permit which at that time included the area currently referred to as Diamba Sud.

Between 1997 to 1998, Ashanti Goldfields completed further exploration activities as part of a similar joint venture with Iamgold.

Between 1999 to 2014, Iamgold conducted exploration activities at the Diamba Sud Project, either individually or as part of a joint venture. The area was relinquished as part of a renewal process for Bambadji and acquired by Boya in 2015.

The Diamba Sud Project is a part of the West Africa craton (WAC) within the Loulo Mining district.

The geology local to the Diamba Sud Project is dominated by plutons belonging to the Falémé Volcanic Belt as well as roof pendants and xenolith screens of the Bambadji Formation which also uncomformably overly the Kofi series sediments that subcrop to the east.

At the westernmost extent of the Kofi series, north striking altered marbles and strongly abilitized lithologies with identified and unidentified protoliths are prevalent. The Kofi series in the area is dominated by undifferentiated sandstones and siltstones with minor conglomerate and breccia. Several dolerite dykes of various orientations intrude the Kofi series and plutonic rocks of the Falémé Volcanic Belt.

The Falémé Volcanic Belt within and surrounding the permit area is made up of the Highway pluton and a range of smaller plugs and dykes. The Balangouma Pluton and heterogeneous granitoids adjacent to it occur to the north of the permit, with the Boboti and Garaboureya plutons outcropping to the south of the permit. The Bambadji Formation is also mapped to subcrop within and surrounding the permit, forming xenolithic screens and roof pendants within the Falémé Volcanic Belt, as well as unconformably overlying the Kofi series to the east.

Iron endo- and exoskarns, some structurally controlled along faults, occur within the Falémé Volcanic Belt, the Bambadji Formation and on western portions of the Kofi series. A genetic link between iron skarn mineralization and gold mineralization has been proposed based on the proximal locations of these deposits, the involvement of high temperature FeCl₂-rich brine and from mineral paragenesis at the Sadiola deposit. Additionally, the Karakaéné Ndi iron skarn, north of Afrigold’s Karakaéné mine, has been a target of significant artisanal workings. Named iron skarns inside and within the vicinity of the project include the Karakaéné Mbah, Karakaéné Ndi and Kouroudiako iron skarns, with other unnamed skarns of various volumes also outcropping in the region.

Sedimentary sequences not confirmed to belong to the Bambadji Formation and possibly belonging to the Kofi series or part of the Diale-Dalema Basin are also present within the permit. These consist of marls, carbonates, polymictic matrix-supported conglomerates and intensely hydrothermally altered lithologies, some of which the protoliths cannot be identified. Granites belonging to the Falémé batholith intrude into these sedimentary units.

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

Both the Falémé batholith and sedimentary sequences are intruded by late predominantly sub-vertical diorite dykes. A number of iron endo and exoskarns also occur in the area and these form prominent topographic highs inside and outside of the permit area.

Exploration has identified seven gold deposits and several prospects located in the DS1 block. These include the deposits of Area A, Area D, Karakara, Kassassoko, Western Splay, Moungoundi, and Southern Arc, as well as the Gamba Gamba North, Area A North, Area D South, and Kouroudiako prospects.  These deposits all form part of a single mineralizing system with local variability influenced mainly by intensity of brecciation, alteration and later supergene processes. The Bougouda prospect is located in the DS2 block.

Mineralization at Diamba Sud is relatively simple, consisting dominantly of pyrite with minor chalcopyrite and magnetite.

There does not appear to be a preferential host lithology, with gold mineralization hosted in most rock types, except for weakly altered fine grained sedimentary rocks. Most of the mineralization is hosted in a combination of disseminated pyrite, minor veinlets and hydrothermal breccia cement.

The predominant mineralization style is orogenic lode gold with supergene enriched saprolite zones specifically in Area D. This style of mineralization can occur as veins or disseminations in altered (often silicified) host rocks or as pervasive alteration over a broad zone. Across Diamba Sud gold mineralization is controlled by a variety of minor structures and often along lithological boundaries.

Gold mineralization is both structurally and lithologically controlled and can occur within granites, argillites, conglomerates, marls and carbonates. Supergene enrichment of the orogenic gold deposits (saprolitic) has also taken place within the permit, with significant mineralization of this style present within Area D.

Most of the mineralization at Diamba Sud is hosted within sedimentary units, where structures that acted as fluid conduits intersected the units allowing fluid flow. Hydrothermal breccia zones within Area A host some of the highest grades within the hypogene mineralized zones from Diamba Sud. The high permeability and porosity of these rocks, in addition to friction and attrition generated at clast boundaries due to strain, allowed fluid to move into this unit and deposit the auriferous pyrite. A precursor phase of albitization and hematization prepared the breccias for a later phase of auriferous pyrite–hematite–albite–carbonate–quartz mineralization.

Mineralized structures also occur throughout the intrusions in the area, with auriferous pyrite ± carbonate veins exploiting shear zones that cut through the granitoids.

Gold mineralization at Diamba Sud is considered to be of the orogenic type.

From 1993 to 1996, Anmercosa conducted regional exploration activities over the Bambadji, Daorala and Boto Project areas as part of a joint venture agreement with Iamgold. These activities included airborne geophysical surveys along with regional and local geochemistry and early drilling activity. No drilling was conducted on the Diamba Sud area.

Ashanti Goldfields also worked on the Bambadji, Daorala and Boto areas and continued to focus on geochemical data acquisition of and conducted some preliminary trenching and pitting in 1997 and 1998.

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

From 1999 to 2014, Iamgold conducted limited prospecting activity over the Bambadji permit: the majority of the work conducted was on the eastern portion of the permit and not on the Diamba Sud area. The western part of the Bambadji permit was relinquished in 2014.

The Diamba Sud exploration permit was granted in April 2015 to Boya, a subsidiary of Boya Gold PTY Ltd. (Boya Gold). During the period 2015-2016, Boya conducted regional soil geochemistry for gold using a 400 x 400 m grid, later infilled to 200 x 100 m in places, collecting 1,552 soil samples. Outcrop mapping was completed over an area of 37 km² and 96 grab samples were collected.

Air core and reverse circulation (RC) drilling was conducted by Minerex drilling. A total of 334 air core holes with depths from 2–56 m were drilled for a total meterage of 3,358 m with 1,160 samples, including quality control samples, sent to the SGS laboratory in Bamako (SGS Bamako) for analysis. In addition, 9 RC holes, with maximum depths ranging from 40–86 m, were drilled over two target areas in the south of DS1 at Dembakholi and Southern Arc for a total meterage of 650 m with 338 samples, including quality control samples, sent to SGS Bamako for analysis.

Boya Gold was acquired by Chesser Resources Ltd. (Chesser) in 2017. Chesser commenced RC drilling in 2019 using several different drilling contractors during various campaigns through to July 2023. A total of 10 geochemical targets were drilled by RC or RC with a core tail, totaling 493 holes and 58,960 m. In total, 127 diamond drill (DD) holes totaling 19,805 m were drilled between November 2019 and July 2023. All holes were sampled at 1- or 2-m intervals in the oxide material and at 1-m intervals in the fresh rock and all samples were submitted to SGS Bamako or to the ALS laboratory in Burkina Faso.

After acquiring Chesser in 2023, Fortuna began an extensive program of verification and infill drilling across nine of the advanced target areas with the aim of collecting sufficient data to support the estimation of Mineral Resources. A total of 532 RC holes totaling 59,701 m, 425 DD holes totaling 56,672 m and 15 RC with DD tail holes totaling 1,830 m were drilled between October 2023 and October 31, 2025.

RC drilling was conducted using an Atlas Copco T3W rig with a 950CFM compressor and an Atlas Copco Hurricane booster. All holes were cased with PVC to 6 m and then drilled using a 5.5-inch RC hammer bit. Samples were collected at 1-meter intervals from an onboard cyclone then split on site to produce two 1.5 kg samples, the first sample was submitted for analysis, the second stored as a duplicate sample.

Diamond drilling was conducted with Atlas Copco CS14 and CT14 diamond drill rigs, dependent upon the contractor. The majority of this drilling is drilled to HQ (63.5 mm core diameter) and NQ (47.6 mm) sizes. In Area D where the oxide material can be difficult to keep holes from collapsing, holes are drilled PQ (85 mm) from surface to fresh rock before stepping down to HQ and NQ as appropriate to conditions and depth.

Proposed surface drill hole collar coordinates, azimuths and inclinations were designed based on the known orientation of mineralization and the planned depth of intersection using geological plan maps and sections as a guide. The location of the collar is defined in the field using differential global positioning system (GPS) instruments. The drill pad is then prepared at this marked location. Upon completion of the drill hole, a survey of the collar is performed using Total Station equipment, with results reported in the collar coordinates using reference Datum WGS84, UTM Zone 29N.

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

The geologist in charge of drilling is responsible for orienting the azimuth and inclination of the hole at the collar using a compass clinometer. Downhole surveys for RC holes are completed every 10 m by the drilling contractor using a Reflex Gyro Sprint IQ survey tool. Downhole surveys of the DD holes were conducted using a variety of survey tools, as there were several rigs operating at the same time in different areas. These included a Reflex EZ Shot TM, the Reflex Gyro Sprint IQ and an Axis Champ gyro. Readings were collected every 30 m down the hole. Boya assesses the downhole survey measurements as a component of data validation.

Drill holes are typically drilled on sections spaced 25 to 50 m apart along the strike of the mineralized structures.

The Area A deposit has been drilled over an approximate area of 700 m (north to south) and 500 m (east to west) to depths around 280 m from surface. Exploration drilling has increased in depth to the south.

The Area D deposit has been drilled over an approximate area of 600 m (north to south) and 700 m (east to west) to depths around 250 m from surface. Exploration drilling has increased in depth to the south.

The Karakara deposit has been drilled over a strike length of approximately 1,000 m (north–northeast to south–southwest) and to depths of 230 m from surface. Exploration drilling has increased in depth in response to the plunge of the mineralization to the southwest.

The Kassassoko deposit has been drilled over an approximate area of 700 m (southwest to northeast) and 200 m (southeast to northwest) to depths around 150 m from surface. Exploration drilling has increased in depth to the south.

The Western Splay deposit has been drilled over an approximate area of 500 m (north to south) and 700 m (east to west) to depths around 280 m from surface. Exploration drilling has increased in depth to the south.

The Moungoundi deposit has been drilled over a strike length of approximately 400 m (north to south) and to depths around 150 m from surface.

The Southern Arc deposit has been drilled over a strike length of approximately 800 m (northwest to southeast) and to depths of 200 m from surface.

The Bougouda prospect has been drilled over a strike length of approximately 1,800 m (northeast to southwest) and to depths of 150 m from surface.

The Gamba Gamba North prospect drilled by Chesser is split into two main mineralized zones. The eastern zone has been drilled over a strike length of 300 m (north–northeast to south–southwest) to a depth of 150 m from surface; the western zone has been drilled over a strike length of 300 m (north to south) to a depth of 125 m from surface. The drilling follows the plunge of the mineralization, generally getting deeper towards the south–southwest.

The Bougouda prospect has been drilled over a strike length of approximately 1,800 m (northeast to southwest) and to depths of 150 m from surface.

The relationship between the sample intercept lengths and the true width of the mineralization varies in relation to the intersect angle and sometimes can be difficult to determine based on the various orientations of the mineralized structures. Calculated estimated true widths (ETWs) are always reported together with actual sample lengths by

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

taking into account the angle of intersection between drill hole and the mineralized structure.

RC chips were collected and logged at the drill site and stored in standard chip trays for further investigation as appropriate.

Core is logged in detail at the field camp, using LogChief software and transferred electronically to DataShed 5 for database management. As is the norm with exploration drilling, geological logging is undertaken at several different times to ensure that a level of consistency is maintained. Lithologies, alteration, mineralization and structures are all logged to industry standards. Geotechnical information collected routinely is at a rudimentary exploration level, however 14 holes (2,100 m) were fully logged to higher geotechnical standards as part of geotechnical studies.

The sampling methodology, preparation, and analyses differ depending on whether it is DD core or RC chip samples.

Sampling of RC holes is conducted at the drilling rig with one split sample collected for routine analysis and the second sample split again for duplicate sample submission.

Sampling of diamond core is conducted after geological logging and marking of the core for sampling. Core is split using a diamond saw. The half core that does not contain the orientation line is then selected for sampling. Intervals are based upon geology with nominal sample lengths of 1 meter due, although this may be variable, but standard sampling procedures dictate a minimum sample length of 0.4 m and a maximum of 1.2 m. For duplicate samples only, the remaining half core is cut in half again for submission to the laboratory.

PQ core is sampled as quarter core for routine sample submission and the second quarter is collected for duplicate sample submission.

All samples are combined into batches for submission to the laboratory. Nominally each batch should represent a specific hole, however the preferred batch size at the laboratory is 100 samples, thus longer holes tend to be split into two or three batches. Once sampled and labelled samples are packed into large sacks and sealed ready for transportation.

Sample collection and transportation of drill core and chip samples is the responsibility of Boya exploration and must follow strict security and chain of custody requirements established by Fortuna. Samples are retained in accordance with the Fortuna corporate sample retention policy.

The preparation of both RC and DD samples is conducted by ALS Global at their preparation facilities in Kédougou, Senegal or Bamako, Mali.

Samples from Diamba Sud are assayed for gold at ALS Global’s analytical facility in Ouagadougou, Burkina Faso or the SGS Mineral Services laboratory in Bamako, Mali. The assay method used for all the drill samples is a fire assay fusion with atomic absorption spectroscopy (AAS) finish. Both the ALS Global and SGS Mineral Services laboratories are certified for the preparation and assaying of gold samples.

Implementation of a quality assurance/quality control (QAQC) program is current industry best practice and involves establishing appropriate procedures and the routine insertion of certified reference material (CRMs), blanks, and duplicates to monitor the sampling, sample preparation and analytical process. Fortuna implemented a full QAQC program to monitor the sampling, sample preparation and analytical process for all drilling campaigns in accordance with its companywide procedures. The program involved the routine insertion of CRMs, blanks, and duplicates. Evaluation of the QAQC

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

data indicates that the data are sufficiently accurate and precise to support Mineral Resource estimation.

Site visits were completed. The QPs individually reviewed the information in their areas of expertise, and concluded that the information supported Mineral Resource estimation, and could be used in mine planning and in the preliminary economic analysis that supports the PEA.

Maca Interquip Mintrex (MIQM), previously Mintrex, was engaged by Chesser in May 2022 and subsequently by Fortuna to manage metallurgical testwork for the Diamba Sud Project. The testwork was undertaken by ALS Metallurgy Pty Ltd (ALS) in Perth, Western Australia. A testwork program developed by MIQM aimed to build upon the initial scoping study level testwork competed in 2022. The testwork was conducted on samples selected by MIQM and Fortuna across three initial deposits: Area A, Area D, and Karakara. The purpose of the testwork program was to provide inputs to future studies for a gold processing plant.

Testwork was to be conducted in five stages. The first stage was comminution testwork, which was used to determine the mineralization properties. Optimization tests were then conducted in the second stage to determine optimum conditions for cyanidation. The third stage of testwork determined cyanidation at the optimized conditions and carbon testing across a number of samples. The final two stages consisted of variability testing. Bulk mineral analysis (BMA), rheology and diagnostic leach tests were added during the program to investigate flow properties and speciation. Additional testwork was commissioned and managed by Fortuna covering the Western Splay, Kassassoko, Moungoundi and Southern Arc deposits, as well as some supporting testwork identified during review. This additional testwork was completed in phases through 2024 and 2025.

The testwork program indicated favorable grinding and leaching characteristics for the oxide mineralization and most samples of the fresh mineralized material:

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

Mineral Resource estimates used diamond and RC drill hole information obtained by Boya since 2019. Mineralized domains identifying potentially economically extractable material were modeled and used to code drill hole samples for geostatistical analysis, block modeling and grade interpolation. Gold and copper grades were estimated into a geological block model consisting of either 5 x 5 x 5m or 10 x 10 x 5 m selective mining units (SMUs), depending on the level of data density. Grades were estimated by ordinary kriging (OK) and constrained within an ultimate pit shell based on estimated long term metal prices, projected operating costs, geotechnical constraints, and metallurgical recoveries. Estimated grades were validated globally, locally, and visually prior to tabulation of the Mineral Resources.

Resource confidence classification considers a number of aspects affecting confidence in the resource estimation including; geological continuity and complexity; data density and orientation; data accuracy and precision; and grade continuity. Mineral Resources are categorized as Indicated or Inferred. The criteria used for classification includes the number of samples, spatial distribution, distance to block centroid, kriging efficiency (KE) and slope of regression (ZZ).

The Qualified Person for the Mineral Resource estimate is Mr. Eric Chapman, P.Geo., a Fortuna employee. Mineral Resources for the Diamba Sud Project are reported insitu, using the 2014 CIM Definition Standards, and have an effective date of July 7, 2025. Mineral Resources that are not Mineral Reserves do not have demonstrated economic viability. The estimate is detailed in Table 1.1.

Table 1.1 Mineral Resources for the Diamba Sud Project

Notes to accompany Mineral Resource table:

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

Factors that may affect the estimates include metal price and exchange rate assumptions; changes to the assumptions used to generate the cut-off grades; changes in local interpretations of mineralization geometry and continuity of mineralized zones; changes to geological and mineralization shape and geological and grade continuity assumptions; variations in density and domain assignments; geometallurgical assumptions; changes to geotechnical, mining, dilution, and metallurgical recovery assumptions; change to the input and design parameter assumptions that pertain to the conceptual open pit constraining the estimates; extent of artisanal mining; and assumptions as to the continued ability to access the site, retain mineral and surface rights titles, maintain environment and other regulatory permits, and maintain the social license to operate.

There are no other known environmental, legal, title, taxation, socioeconomic, marketing, political or other relevant factors that would materially affect the estimation of Mineral Resources that are not discussed in this Report.

The Diamba Sud Project has no defined Mineral Reserves

The mine plan is partly based on 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 PEA based on these Mineral Resources will be realized. Mineral Resources that are not Mineral Reserves do not have demonstrated economic viability.

Mining is proposed for Mineral Resources defined inside an ultimate pit shell based on a long term gold metal price of US$2,300/oz, by conventional open pit mining methods and equipment, using the services of a mining contractor.

There will be seven open pits (Area A, Area D, Karakara, Western Splay, Kassassoko, Moungoundi and Southern Arc). The Area D pit will be mined in two stages, the other pits will be mined in a single stage.

The overall mining and production strategy is to maintain a mill processing throughput of 2.0–2.5 Mtpa. The processing plant design capacity is 2.0 Mtpa of fresh rock, with capacity to process up to 2.5 Mtpa where the blend is 80% fresh rock and 20% oxidized rock. The pits were sequenced to maximize the amount of oxide mined early in the schedule to maximize processing rate and cashflow early in the schedule. The mine life based on Indicated and Inferred Mineral Resources is 8.1 years.

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

Drilling and blasting are planned for oxide, transitional and fresh mineralized material and waste, followed by conventional excavator and truck operations within the pits for the movement of mineralized material and waste. Free digging will be conducted in the oxide zones if practical, otherwise blasting has been assumed for all the weathering horizons. Bench heights for extraction of mineralized material and waste material is 5 m taken in two digging flitches of 2.5 m. Where possible in high waste stripping pit stages, 10 m bench heights will be used at an appropriate standoff distance from known mineralization.

Mining costs and equipment requirements are predominantly based on a request for pricing conducted in 2025 with five mining contractors submitting proposals however only three were used for pricing after outliers were removed. The mining equipment is proposed to be 120 t and 200 t excavators, along with 100 t haul trucks. The annual rate of mining movement peaks at 9 million bank cubic meters (BCM). A common pool of equipment will be used and scheduled across all of the active pits so that movement between the pits is minimized.

A tender process will be used to select the mining contractor.

Run of mine (ROM) material will be trucked from the pits to the ROM pad and tipped onto the ROM pad to be reclaimed and loaded to the crusher feed bin using front-end loaders that will be operated by the mining contractor.

The process plant design is based on a metallurgical flowsheet envisioned for the production of gold doré at optimum recovery while minimizing initial capital expenditure and operating costs. The flowsheet comprises a conventional crushing, milling, gravity recovery, a CIL, carbon elution and gold recovery circuit.

The key project design criteria for the plant are:

The proposed process design is comprised of the following circuits:

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

The Project has sufficient surface area to accommodate all infrastructure requirements to support the open pit life-of-mine (LOM) and sufficient studies have been completed to ascertain reasonable locations for all major infrastructure to PEA study level.

The proposed TSF will be located approximately 5 km to the north of the process plant. The Stage 1 tailings facility has a design capacity of 2.4 Mt, sufficient to handle tailings for 12 months based on design production levels, expansion of the facility has been designed annually thereafter. There is sufficient room for expansion of the tailings facility for the proposed life of mine (17.8 Mt), based on the design production rates.

The recommended power option for the operation is heavy fuel oil (HFO) generator(s) power for the site. Senegal does not have a feasible grid connection within proximity of the Project. As studies progress the addition of solar photovoltaic and a hybrid power solution will be assessed. Under average conditions, water demand is estimated at 66 L/s. Approximately 80% of the water in the slurry deposited into the TSF can be recovered from the TSF and pumped back to the plant for reuse in the process.

No market studies have been performed as part of this PEA. Diamba Sud will produce gold doré, which is readily marketable on an ‘ex-works’ or delivered basis to several refineries in Europe and Africa. There are no indications of the presence of penalty elements that may impact on the price or render the product unsalable.

The long-term gold price used for estimating potential mineralized material in the LOM plan was US$2,300/oz, based on the mean consensus prices from 2026 to 2028 of US$2,726/oz weighted at 40% and a 5-year historical average of $2,023/oz weighted at 60%. An elevated gold price of US$2,600/oz, using a 15% upside was used for Mineral Resource estimation. The economic analysis conducted in October 2025 used a base case gold price of US$2,750/oz.

The QP has reviewed the information provided by Fortuna on marketing, contracts, metal price projections and exchange rate forecasts and notes that the information provided support for the assumptions used in this Report and are consistent with the source documents, and that the information is consistent with what is publicly available within industry norms.

In April 2015, Boya entered into a Mining Convention (Mining Agreement) with the State of Senegal. This was followed by the grant of the Diamba Sud exploration permit in June 2015. The exploration permit was granted for an initial period of three years, subject to being renewed twice for additional periods of three years. It was last renewed on June 9,

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

2021, for a period of three years, being the second and final renewal which expired on June 9, 2024. However, Boya obtained a special two-year retention period until June 21, 2026 in order to complete the works necessary for a PEA, and to conduct the environmental studies that are required in support of an application for a mining license. Boya must submit an application for an exploitation permit before the aforementioned date and at least four months before the expiry of the exploration permit.

The environmental and social baseline has been established for the Project with field studies undertaken by Earth Systems, an environmental and social science and engineering company based out of Australia and registered in Senegal since 2022, with support from Oryx Expertise in 2024, a specialized biodiversity consultancy firm. These studies have included those related to socio-economic conditions, land and water use, surface and groundwater resources, terrestrial and aquatic ecology and biodiversity, air quality, noise and vibration, climate change, traffic and transportation, as well as archaeology and cultural heritage.

Senegalese law requires an Environmental Permit for the Diamba Sud Project before an Exploitation Permit can be obtained. Earth Systems was commissioned to prepare an Environmental and Social Impact Assessment (ESIA) in compliance with Senegalese regulatory requirements, and in accordance with international best practices such as the Equator Principles and International Finance Corporation (IFC) Performance standards.

The ESIA identifies and assesses the potential impacts of the Project and develops environmental and social management plans designed to mitigate impacts and enhance local benefits, such as environmental and social management plan, stakeholder engagement plan, capacity building plan, livelihood restoration program, mine rehabilitation and closure plan and a voluntary environmental and social investment program.

Regular consultations with Senegalese government authorities, local communities and other stakeholders have been conducted since the start of the Project to ensure that stakeholders' interests are taken into account in the planning and development of the project. In 2025, formal consultations were held to present the Project as defined in this Report.

The ESIA was submitted to the Direction de la Réglementation Environnementale et du Contrôle (DiREC), a division of the Ministry of the Environment and Sustainable Development of Senegal on October 6, 2025, for approval, with a decision expected in early 2026.

From an environmental perspective, artisanal mining is identified as the main threat to biodiversity in the study area. Artisanal mining activities have decreased over the past years in the Project area due to the current legal exploration activities ongoing. There are no artisanal mining activities or settlement in the Project development or fenced in area at the effective date of the Report.

The capital cost estimate is based upon an engineering, procurement and construction management (EPCM) approach where the Owner assumes the builder’s risk. As a result, the cost estimate does not include a builder’s margin. The estimate is considered to have an accuracy range of ±25 to –30%.

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

Capital and operating cost estimates are based on established cost experience gained from engineering house experience, projected budget data and quotes from manufacturers and suppliers.

Capital costs include all investments in ongoing mine development, infill drilling, mine equipment overhaul and components, and infrastructure necessary to sustain the continuity of the operation.

Mine development includes the main development and infrastructure of the mine as this activity has the objective of increasing confidence in currently defined Mineral Resources.

Mine closure costs are attributed to site rehabilitation costs required to remediate the area where the mine is located and to meet mine closure requirements.

Equipment and infrastructure costs are attributed to all departments of the Project including mine, plant, tailing facilities, maintenance and energy, safety, information technology, administration and human resources, logistics, camps, geology, planning, laboratory and environmental.

The capital cost estimate is summarized in Table 1.2.

Table 1.2 Summary of Projected Major Capital Costs for the LOM

Projected sustaining capital costs for the proposed LOM are summarized in Table 1.3, and total US$48 million.

Table 1.3 Summary of Projected Major Sustaining Capital Costs for the LOM

Long-term projected operating costs are based on the LOM mining and processing requirements.

Operating costs include site costs and operating expenses to maintain the operation. These operating costs are analyzed on a functional basis, and the cost structure is not similar to the operating costs reported by the financial statements published by Fortuna.

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

Site costs relate to activities performed on the property including mine, plant, general services, and administrative service costs. Other operating expenses include costs associated with transportation and community support activities.

Direct operating costs are estimated as $51.16/t of material milled or $1,081/oz of gold produced, as summarized in Table 1.4.

Table 1.4 Life-of-Mine Operating Costs

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, there is no certainty that the PEA results will be realized. Mineral resources that are not mineral reserves do not have demonstrated economic viability.

The Diamba Sud Project has been evaluated on a discounted cash flow (DCF) basis. The results of the analysis show the project to potentially be economically very robust (Table 1.5). The economic analysis assumes that Fortuna will provide all development funding via inter-company and shareholder loans to the mine operating entity, which will be repaid with interest from future gold sales.

Table 1.5 PEA Summary

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

Note: (1)  This is a non-IFRS financial measure. The definition and purpose of this non-IFRS financial measure is included under the heading “Cautionary Note on Non-IFRS Measures” in this Report. Non-IFRS financial measures have no standardized meaning under IFRS and therefore, may not be comparable to similar measures presented by other issuers.

The pre-tax net present value with a 5% discount rate (NPV_5%) is $772 million and with an IRR of 86% using a base gold price of $2,750/oz. The post-tax Project NPV_5% is $563 million, with an IRR of 72% and a payback period of less than one year at a gold price of $2,750/oz. The payback period is defined as the time after process plant start-up that is required to recover the initial expenditures incurred developing the Diamba Sud Project.

Like most gold mining projects, the key economic indicators of NPV_5% and internal rate of return (IRR) are most sensitive to changes in gold price. A $250/oz reduction in the gold price reduces Fortuna’s after-tax NPV_5% by $119 million and the IRR by 13%. A $250/oz increase in the gold price increases Fortuna’s NPV_5% by $119 million and the IRR by 13%.

Project IRR is most sensitive to changes in revenue parameters (i.e. gold price and gold grade) and operating costs, while changes to recovery and capital costs are secondary.

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

The PEA was based on Mineral Resources that have been estimated using industry-recognized methods, and estimated operational costs, capital costs, and plant performance data. The economic analysis indicates a positive cash flow using the assumptions and parameters detailed in this Report.

A number of opportunities and risks were identified by the QPs during the evaluation of the Diamba Sud Project.

Opportunities include:

Risks include:

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

The following recommendations outline the key activities required to advance the Diamba Sud Project from the PEA to a more advanced study level. The focus is on resource expansion and infill, technical de-risking, design optimization, and confirmation of environmental, permitting, and social frameworks. The next phase of work is broken into activities relating to exploration, growth and infill, and those optimizing and advancing technical studies to support project development. All recommended programs are independent and may be executed concurrently unless otherwise stated.

An exploration and infill drilling program is recommended to expand the existing deposits that have not been fully defined and potentially support upgrading of Inferred Mineral Resources to Indicated Mineral Resources.

Key priorities for the exploration program include:

The budget to execute the exploration and infill program is estimated at approximately US$10.1 million based on current contracted drill rates and in-country expenses. The program for 2026 will include, but not be limited to:

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

Recommendations to improve geotechnical data confidence and support pit design optimization for the Western Splay, Kassassoko, Southern Arc, and Moungoundi pits as follows:

An allocation of approximately US$500,000 has been made for the geotechnical investigation program, comprising both technical studies and physical drilling activities.

Technical studies and analysis are budgeted at approximately US$250,000, covering project supervision and reporting, televiewing, laboratory rock strength testing, and interpretation of results.