Fortuna Mining Corp. (NYSE: FSM) (TSX: FVI) is pleased to announce it has entered into an earn-in agreement with Qstone Inc., a private Guyanese company, pursuant to which Fortuna may earn up to a 70% interest in the Quartzstone Project, a large land package comprising 29,600 hectares located in the greenstone belt of north central Guyana.

Jorge A. Ganoza, President and CEO of Fortuna, commented, “We are excited to establish a presence in the Guyana Shield, a highly prospective region with a strong history of gold discoveries.” Mr. Ganoza continued, “The Quartzstone Project, where historical drilling has identified multiple high grade zones of near-surface gold mineralization, is located in a prolific exploration camp, and this transaction provides Fortuna with a staged path to unlock its potential through systematic exploration and drilling.”

Previous Drill Highlights

A total of 183 diamond core drill holes, comprising 23,190 meters, were completed between 2010 and 2017. Drilling along a five-kilometer corridor identified multiple zones of high grade near-surface gold mineralization. Drill highlights include:

Refer to Appendix 1 for full details of the drill holes and assay results for this historical program.

Project location and geological setting

Figure 1: Location of Quartzstone Project, Guyana

The Quartzstone Project is located approximately 120 kilometers west of Georgetown and 35 kilometers northwest of G Mining’s Oko West project (refer to Figure 1). The Project hosts an orogenic gold system along the contact between a granitoid complex and Lower Proterozoic greenstone rocks within the Guyana Shield, a geological setting known for significant gold deposits.

Local geology comprises granitoids, metavolcanic, and metasedimentary rocks, cut by a west-dipping, north-south striking thrust and shear zone that extends over 26 kilometers. Gold mineralization is hosted in quartz-tourmaline-carbonate veins and breccias within a high-strain corridor up to 100 meters wide along the principal north-south shear and associated northeast-trending structures. Drilling to date has tested only approximately 5 kilometers of the 26 kilometer shear zone within the concession area. Several geochemical anomalies along northeast-southwest trending cross-structures also remain untested and will be prioritized by the exploration program.

Planned Exploration

Fortuna’s initial exploration program, budgeted at approximately US$5.5 million, will focus on advancing priority targets already defined at Quartzstone, while generating additional targets along the highly prospective 26 kilometer main shear zone. Planned work includes airborne magnetic surveys to develop a detailed structural framework, supported by high-resolution satellite imagery and digital elevation modelling. Field programs will include infill geochemical sampling, auger drilling, and detailed geological and regolith mapping over prospective geophysical targets and known anomalous areas. An initial 5,000 meter diamond drilling program is planned to test historical targets and workings, as well as priority structural corridors along the main contact and northeast-trending intersections.

Earn-in Agreement Terms

Fortuna may earn an initial 51% interest in the Quartzstone Project by completing a minimum of 60,000 meters of drilling within four years, while paying all license fees and funding all related expenditures. Upon exercise of the first option, Fortuna will form a joint venture with Qstone.

Fortuna may earn an additional 19% interest in the Qu artzstone Project, for an aggregate 70% interest, by solely funding a feasibility study within three years of exercising the first option and continuing to pay all license fees. Upon signing the Earn-In Agreement, the Company paid Qstone a non-refundable cash option premium of US$5 million.

In addition to royalties payable to the State on gold production, the Quartzstone Project is subject to a 4.5% net smelter returns royalty in favour of a prior owner, which may be repurchased at a price to be determined by the parties at any time.

Quality Assurance & Quality Control for previous exploration drill program

All diamond drilling (DD) drill holes started with PQ sized diameter (85 mm core), before reducing to HQ diameter (63.5 mm core) diamond drill bits on intersecting fresh rock. The core was logged, marked up for sampling using standard lengths of one meter or to a geological boundary. Samp les were then cut into equal halves using a diamond saw. One half of the core was left in the original core box and stored in a secure location at the core yard at the project site. The other half was sampled, catalogued, and placed into sealed bags and securely stored at the site until shipment.

All DD samples were prepared by WBDG at the in-house sample preparation facility at the Quartzstone camp where samples were dried and crushed to 95% passing a 10-mesh screen. Following crushing, samples were riffled to 500 gram and pulverised to 80% passing a 150-mesh screen to produce a final 50-gram pulp sample.

Prior to 2013, pulps were securely transported to either Loring Laboratories Ltd., in Georgetown, Guyana, or Acme laboratory located in Santiago, Chile, for assay analysis. Samples were analyzed by fire assay using 50 gram sample charge with atomic absorption spectroscopy finish. If the result was >1.0 g/t Au the sample was re-ass ayed by fire assay with gravimetric finish.

The 2013 exploration program used the Acme Laboratory in Abidjan, Ivory Coast, and ALS Laboratory in Lima, Peru. Acme assayed samples using the bulk leach extractable gold method with solvent residue assayed using a standard fire assay with atomic absorption spectroscopy finish using 50 gram sample charges. ALS used gold by bulk extended leach cyanide using 1 kilogram sample charges.

Since 2015 Activation Laboratories Canada (Actlabs), with a laboratory in Georgetown, Guyana, used for analysis by fire assay with gravimetric finish and leachwell 500 gram sample charges. In 2016 Actlabs were used for re-analysis of rejects by leachwell 500 gram sample charges. The 2017 drilling was analyzed at Actlabs in Georgetown, Guyana, by metallic screens and fire assay with gravimetric finish.

Quality control procedures included the systematic insertion of blanks, duplicates and sa mple standards into the sample stream. In addition, the laboratories inserted their own quality control samples.

Qualified Person

Paul Weedon, Senior Vice President, Exploration for Fortuna Mining Corp., is a Qualified Person as defined by National Instrument 43-101 being a member of the Australian Institute of Geoscientists (Membership #6001). Mr. Weedon has reviewed and approved the scientific and technical information contained in this news release. Mr. Weedon conducted a site visit to the Quartzstone Project in June 2025, where mineralized intervals of drill core were examined; surface exposures of mineralization were visited, and discussions held with geology staff regarding historical sampling and analytical techniques underlying the drilling data. To further verify the data, original assay certificates were compared to the database and independent sampling of core was performed that confirmed the presence of go ld in randomly selected mineralized intervals. There were no limitations to the verification process.

About Fortuna Mining Corp.

Fortuna Mining Corp. is a Canadian precious metals mining company with three operating mines and a portfolio of exploration projects in Argentina, Côte d’Ivoire, Mexico, and Peru, as well as the Diamba Sud Gold Project in Senegal. Sustainability is at the core of our operations and stakeholder relationships. We produce gold and silver while creating long-term shared value through efficient production, environmental stewardship, and social responsibility.

Appendix 1: Quartzstone historical program drill holes and assay results

<sup>Notes:
1. EOH: End of hole
2. Depths and widths reported to nearest significant decimal place
3. NSI: No significant intercepts
4. True widths cannot be estimated currently, as the orientation of mineralization is unknown.
5. RC: reverse circulation drilling | DD: diamond drilling tail | RCD: reverse circulation drilling with diamond tail</sup>