Exhibit 99.1

Diamba Sud Gold Project,

Kédougou Region, Senegal

Technical Report,

Effective Date: June 30, 2026

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 estimation of current and future Mineral Resources and Mineral Reserves at the Project; the Company’s ability to convert Mineral Resources into categories of higher geological confidence or Mineral Reserves; the Government’s plans to transform the airfield in Kédougou to an international airport; the proposed mining methods and production of gold doré, including projected mill throughput, the movement and extraction of mineralized material and waste, projected mining equipment and personnel requirements, processing and recovery methods, proposed infrastructure to support the open pit life-of-mine; the projected initial capital and sustaining capital required; estimated operating costs; 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, cash costs, all-in sustaining costs (“AISC”), average yearly free cash flow, life of mine unit costs, projected mine life; the project design, including proposed land acquisition and compensation process, the Company’s engagement with artisanal small-scale miners, the tailings storage facility, power sources, water supply and storage, process plant, infrastructure area; and the proposed open pit mine plans; the plans for completing the early works program; the project development timeline to production including certain environmental permits and authorizations required in connection with the operation of the mine, and which are in addition to the Decree for the environmental and social impact assessment (ESIA) which has already been received, the permitting of future phases of the project, obtaining the exploitation permit for the Project and other permitting approvals; the development and construction of a mine and operations at the Project; the establishment of a mine closure plan; the timing of and future prospects for exploration and expansion drill programs; proposed geotechnical work; possible metallurgical testwork; potential studies to optimize and advance the Project.

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, without limitation: the estimation and realization of Mineral Resources and Mineral

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

Reserves, and any potential upgrades of existing Inferred Mineral Resource and Probable Mineral Resource estimates; gold prices, fluctuations in foreign exchange or interest rates; the estimation of initial and sustaining capital requirements; potential changes to the proposed mine design, mining methods, and infrastructure requirements; the estimation of labor and operating costs and 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, and the amount of expenditures thereon; dependence of operations on construction and maintenance of infrastructure; the Company’s ability to maintain existing or obtain all necessary permits, licenses and regulatory approvals, including an exploitation permit, in a timely manner or at all; changes in laws, regulations and government practices, including environmental, tax, export and import laws and regulations; 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 constructing a mine at the Diamba Sud Project and producing gold therefrom; economic and political risks associated with operating in foreign countries, including emerging country risks, exchange controls, expropriation, and corruption; political developments in Senegal being inconsistent with Fortuna’s expectations; increased competition in the mining industry; environmental risks including risks related to climate change; risks related to artisanal mining on the Project, including title disputes or claims, and other similar matters; the risk that the State of Senegal may elect to purchase up to an additional 25% contributory interest in the operating entity; 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, 2025. 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 Forward-looking Information in this Technical Report, whether because of new information or future events or otherwise.

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

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

Technical disclosure regarding the Company’s properties included herein has been prepared in accordance with National Instrument 43-101, Standards of Disclosure for Mineral Projects (“NI 43-101") and the Canadian Institute of Mining, Metallurgy, and Petroleum Definition Standards on Mineral Resources and Mineral Reserves. Canadian standards, including NI 43-101, differ from the requirements of the Securities and Exchange Commission, and information included herein may not be comparable to similar information disclosed by U.S. companies.

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. We believe that, in addition to conventional measures prepared in accordance with IFRS, certain investors use this information to evaluate performance. The data presented is 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 Mr. Ruan Venter, P.Eng., 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. Upon the grant of an exploitation permit to Boya, the State of Senegal (the State or State of Senegal) will require Boya to designate and incorporate a new entity to hold the exploitation permit and operate the Diamba Sud Project. The State of Senegal is entitled to a 10% free carried ownership interest in the operating entity, and Fortuna will indirectly hold the remaining 90% interest. In addition, the State has the right to acquire up to an additional 25% contributory interest in the operating entity at a “fair price” as determined through an independent valuation. The percentage and timing of any such additional contributory interest is subject to negotiation with the State. There can be no assurance that the State’s interest will remain limited to 10%.

The Report discloses Mineral Resource and Mineral Reserve estimates for the Project and the results of a feasibility study (FS) 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

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

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.

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.

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 permit exploration permit (permis de recherche) 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. The exploration permit was renewed for a second time on June 9, 2021, being the second and final renewal and which expired on June 9, 2024. However, Boya obtained a special two-year retention period until June 21, 2026, to apply for an exploitation permit, complete the work necessary to file a FS and file the FS, and to conduct the environmental studies that are required in support of an application for an exploitation permit. Boya applied for an exploitation permit from the Ministry of Energy, Petroleum, and Mines on February 4, 2026, received a formal Decree for the environmental permit for the Diamba Sud Project Boya on June 11, 2026, and obtained an extension to the retention period of the exploration permit of 60 days until August 21, 2026 to file the FS with the Ministry of Mines. The State will then make a decision upon the application to grant the exploitation permit

The permit comprises two blocks, the northern block, DS1 is approximately 46.56 km² in area and the southern block, DS2, is approximately 6.31 km² in area, 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 FS assumes the granting of an exploitation permit which will provide Boya, within the boundaries of its perimeter, on surface and indefinitely in depth, with the exclusive rights to explore, extract and dispose of the nominated mineral commodities specified (in this case, gold).

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

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

The FS assumes that the applicable royalties, taxes, and other fiscal terms payable to the State of Senegal, including the contribution to the social development fund, will be in accordance with the provisions 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.

Royalties that affect the Mineral Resources and 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 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 Daorala and Boto Project permit areas, which at that time included the area currently referred to as Diamba Sud. Activities included airborne geophysical surveys along with regional and local geochemistry and early drilling activity. No drilling was conducted on the Diamba Sud area.

Between 1997 to 1998, Ashanti Goldfields completed further exploration activities as part of a similar joint venture with Iamgold. Ashanti Goldfields also worked on the Bambadji, Daorala and Boto areas and continued to focus on geochemical data acquisition and conducted some preliminary trenching and pitting

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 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

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

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 cropping out 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 area. These consist of marls, carbonates, polymictic matrix-supported conglomerates and intensely hydrothermally-altered lithologies, in some of which the protoliths cannot be identified. Granites belonging to the Falémé batholith intrude into these sedimentary units.

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.

The predominant mineralization style is orogenic lode gold with overprinting supergene-enriched saprolite zones in Area D. Mineralization can occur as veins or disseminations in altered (often silicified) host rocks or as pervasive alteration over a broad zone.

There does not appear to be a preferential host lithology, with gold mineralization (>1 g/t Au) hosted in most rock types, except for weakly-altered fine grained sedimentary rocks, although there is a bias towards hydrothermally brecciated carbonate units. Most of the mineralization is hosted in a combination of disseminated pyrite, minor veinlets, and hydrothermal breccia cement.

Hydrothermal breccia zones within Area A host some of the highest grades within the hypogene mineralized zones from Diamba Sud.

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

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

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 Contractors Ltd. A total of 334 air core holes (3,358 m) with depths from 2–56 m were drilled with 1,160 samples, including quality control samples, sent to the SGS laboratory in Bamako (SGS Bamako) for analysis. In addition, 9 RC holes (650 m), with maximum depths ranging from 40–86 m, were drilled over two target areas in the south of DS1 at Dembakholi and Southern Arc 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 607 RC holes totaling 67,713 m, 533 DD holes totaling 72,054 m and 19 RC with DD tail holes totaling 2,520 m were drilled between October 2023 and January 16, 2026.

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 at PQ size (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.

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

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

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 and Fortuna assessing the downhole survey measurements as a component of data validation.

Drill holes are typically drilled on sections spaced 25–50 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 and the deposit remains open at depth.

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 where it remains open. 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 where it narrows but remains open. Exploration drilling has increased in depth in response to the plunge of 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 and remains open at depth. 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 and remains open along strike and at depth. 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 where it remains open.

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 mineralization, generally getting deeper towards the south–southwest where it remains open.

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 are always reported together with actual sample lengths by 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

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

of consistency is maintained. Lithologies, alteration, mineralization and structures are all logged to industry standards. Geotechnical information collected routinely is at an exploration level, however 14 drill 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, 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 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 by SGS at their preparation facilities in 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 independent, and 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 data indicates that the data are sufficiently accurate and precise to support Mineral Resource and Mineral Reserve estimation.

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

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

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.

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 during 2024, 2025 and 2026.

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

Mineral Resource estimates used diamond and RC drill hole information obtained by Boya and Fortuna 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 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

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

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 and slope of regression

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, exclusive of Mineral Reserves, and have an effective date as at April 10, 2026. 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. Boya has applied for an exploitation permit for the Project, which if not granted will have a material impact on the potential development of the Project.

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

A structured process was applied to convert Mineral Resources to Mineral Reserves, supported by pit shell optimization, detailed open pit designs, mine scheduling, and economic evaluation. Mineral Resources from seven deposits (Area A, Area D, Karakara, Moungoundi, Western Splay, Kassassoko and Southern Arc) have had modifying factors applied for the estimation of Mineral Reserves.

Metal prices used for Mineral Reserve estimation were determined as at April 2026 by the corporate finance department of Fortuna from market consensus. Metallurgical recoveries are based on metallurgical test work conducted on samples obtained since 2022.

Cut-off grades were determined based on all variable and fixed costs estimated for the Project. These include exploitation and treatment costs, general expenses, and administrative and commercialization costs (including doré transportation).

Mineral Reserves for the Diamba Sud Project reported as at April 10, 2026 are reported in Table 1.2.

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

Table 1.2 Mineral Reserves for the Diamba Sud Project

Notes to accompany Mineral Reserve table:

Factors that may affect the estimates include metal price and exchange rate assumptions; changes to the assumptions used to generate the cut-off grades; geometallurgical assumptions; changes to geotechnical, hydrogeological, mining recovery, 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, obtain and maintain environment and other regulatory permits, obtain Ministerial approval to initiate construction and exploitation, and maintain the social license to operate.

Mining is proposed by conventional open pit mining methods and equipment, using the services of a mining contractor. Inferred Mineral Resources contained within the open pits have been treated as waste.

The proposed mining operations will cover seven deposits (Area A, Area D, Karakara, Kassassoko, Moungoundi, Southern Arc, and Western Splay). Area A and Area D will be

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

combined to form a single pit mined in three stages, allowing early extraction of high-value oxide ore, predominantly from Area D. Southern Arc will be mined in three stages forming two separate pits. The Karakara pit will be mined in two stages to enable early access to fresh ore. Kassassoko, Moungoundi and Western Splay will each be mined as single stage pits.

The overall mining and production strategy will be to maintain a mill processing throughput of 2.0–2.5 Mt/a. The processing plant design capacity will be 2.0 Mt/a of fresh ore, with capacity to process up to 2.5 Mt/a where the blend is at least 63% fresh and 37% oxidized ore. The pits were sequenced to maximize the amount of oxide mined early in the schedule to optimize processing rate and cashflow early in the schedule. The mine life is estimated at 9.4 years. The ratio of waste to ore over the LOM is 6.3 to 1.

Drilling and blasting is planned for oxide, transitional and fresh ore and waste, followed by conventional excavator and truck operations within the pits for the movement of ore 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 ore and waste material will be 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 were predominantly based on a request for pricing conducted in 2026. The mining equipment is proposed to be 120 t and 200 t excavators, along with 90 t haul trucks. The annual rate of mining movement will peak at 9 million bank cubic meters. 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 reclaimed and loaded to the crusher feed bin using front-end loaders that will be operated by the mining contractor.

The QP is of the opinion that:

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:

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

The proposed process design consists of the following circuits:

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 FS level.

The proposed TSF will be located approximately 5 km to the north of the process plant. The Stage 1 TSF has a design capacity of 2.4 Mt, sufficient to handle tailings for 12 months based on design production levels, expansion of the TSF has been designed annually thereafter. There is sufficient room for expansion of the TSF for the proposed LOM (20.5 Mt), based on the design production rates.

Power for the Project will be supplied through an integrated hybrid power solution comprising heavy fuel oil (HFO), solar photovoltaic, and battery energy storage system components. The HFO power generation component has been agreed with African Power Services, with integration of the solar farm and battery energy storage system targeted during the first year of operations. Senegal does not currently have a feasible grid connection within proximity of the Project.

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

Under average conditions, water demand is estimated at 59 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 re-use in the process.

The QP considers that all mine and process infrastructure and supporting facilities have been included in the general layout to ensure that they meet the needs of the mine plan and production rate.

No market studies have been performed as part of this FS. 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 Mineral Reserves was $2,900/oz, based on the mean consensus prices from 2027 to 2029 of $4,041/oz weighted at 40% and a five-year historical average of $2,510/oz weighted at 60% and applied and adjustment price reduction of -$200/oz. An elevated gold price of $3,300/oz, using a 15% upside was used for Mineral Resource estimation. The economic analysis conducted in June 2026 used a base case gold price of $3,500/oz.

Contracts for early works are progressing for initial construction, initially for site access roads and new camps, and in evaluation tenders for key infrastructure such as the water storage dam and TSF.

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.

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 be granted 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

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

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.

The ESIA was submitted to the Direction de la Réglementation Environnementale et du Contrôle (DiREC), a division of the Ministry of the Environment and Ecological Transition of Senegal on October 6, 2025 and on June 11, 2026 Boya received a formal Decree which approved the ESIA for the Diamba Sud Project (Decree n°011251 of 22/05/2026 granting the Environmental and Social Compliance Certificate for the Diamba Sud gold project).

In parallel with this ESIA process, Boya undertook FS works on the Diamba Sud Project as described in this Report. The FS resulted in two material design changes to the initial Project design covered by the ESIA. The following new infrastructures added by the FS to the Project design are:

These two new components are expected to require additional environmental and social permitting i.e., impact studies or notices. Relevant national authorities including DiREC have been contacted to clarify the permitting pathway, with permitting deemed feasible and planned to start in the second half of 2026.

The capital cost estimate for the Diamba Sud Project is based on an engineering, procurement, and construction management (EPCM) execution strategy, under which the Owner assumes overall project delivery risk. The estimate is considered to have an accuracy range of ±15%, consistent with a feasibility study level estimate.

The total initial capital cost is estimated at $397.5 million as shown in Table 1.3, comprising $181.7 million for the process plant, prepared by Lycopodium Minerals Canada Ltd. (Lycopodium), and $215.8 million of Owner’s capital (net of sunk capital), developed by Fortuna with support from Knight Piésold and other consultants.

Table 1.3 Summary of Capital Costs

Note: numbers may not sum due to rounding 

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

The capital cost estimate is based primarily on vendor quotations for major equipment and consumables, supplemented by first principles estimating, recent tender pricing, and benchmarking against comparable projects in West Africa and Senegal.

Operating costs, including mining, processing and general and administrative (G&A) costs, are estimated at $59.4/t of ore milled, equivalent to $1,146 per payable ounce of gold sold over the LOM. The LOM operating cost summary is shown in Table 1.4.

Table 1.4 Life of Mine Operating Costs

All-in sustaining costs (AISC), including sustaining capital, closure, royalties and refining, are estimated at $1,322 per payable ounce of gold sold. Sustaining capital costs are shown in Table 1.5.

Table 1.5 Summary of Sustaining Capital Costs over LOM

The capital and operating cost estimates are considered appropriate for a feasibility study level and reflect prevailing cost conditions in West Africa.

The Diamba Sud Project was evaluated on a discounted cash flow (DCF) basis. 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.

The pre-tax net present value (NPV) with a 5% discount rate (NPV_5%) is $1,379 million and with an internal rate of return (IRR) of 70% using a base gold price of $3,500/oz.

The economic analysis is based on the key assumptions summarized in Table 1.6.

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

Table 1.6 Key Economic Model Assumptions

The post-tax Project NPV_5% is $1,009 million, with an IRR of 60% and a payback period of one year at a gold price of $3,500/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.

A summary of the results of the economic analysis are provided in Table 1.7.

Table 1.7 Economic Analysis Summary

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

Notes:

The FS was based on Mineral Reserves 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.

Opportunities include:

Opportunities include:

Diamba Sud Gold Project, Kédougou Region, Senegal Technical Report

Risks Include:

Opportunities include:

Risks include:

Opportunities include: