Fortuna's Deep Sunbird Drilling Program Confirms Exceptional Gold Grades at 492+ Meter Depths

Fortuna Mining Corp. (NYSE: FSM | TSX: FVI) has released compelling results from its ongoing exploration drilling campaign at the Sunbird deposit within the Séguéla Mine in Côte d’Ivoire. The drilling program has successfully traced high-grade gold mineralization to significant depths, with key intercepts revealing premium ore grades that substantially exceed initial expectations. One of the standout results comes from drill hole SGDD148, which encountered 6.1 g/t Au across an estimated true width of 18.9 meters beginning at the 564-meter depth marker, including spectacular 25.4 g/t Au and 27.4 g/t Au intervals at deeper zones.

The deeper exploration zones at approximately 492 meters and beyond are now producing consistently strong assay results. Fortuna currently operates five drill rigs focused on the Sunbird property, marking a significant acceleration of the resource delineation effort. Paul Weedon, Senior Vice President of Exploration, noted that “these drilling results substantiate high-grade ore zones that remain largely unexplored in the deeper portions of the deposit.” The company’s strategy centers on identifying and defining additional ore shoots within the broader mineralized system.

Major Drill Intercepts Reshaping Resource Potential

The current drilling campaign has produced multiple intercepts with exceptional gold grades. Drill hole SGRD2473 intersected 15.4 g/t Au over 4.2 meters (true width) from the 478-meter mark, including a narrower zone grading 26.2 g/t Au. Notably, hole SGRD2491 returned two significant intercepts: 5.2 g/t Au across 8.4 meters from 513 meters depth, and 8.2 g/t Au over 8.4 meters from 528 meters depth. The latter interval contained a spectacular 1.4-meter sub-interval grading 29.6 g/t Au.

The extension drilling has successfully defined mineralization approximately 400 meters beyond the existing Mineral Resource and Mineral Reserve envelopes as outlined in Fortuna’s January 2026 resource update. Drill hole SGDD149 exemplifies this expansion, yielding 13.0 g/t Au across 4.2 meters from 686 meters depth. These results collectively validate the resource expansion thesis and suggest meaningful upside to the current mineral reserve estimate.

Underground Drilling Architecture and Exploration Methodology

Fortuna has implemented a dual-pronged drilling approach combining reverse circulation (RC) and diamond drilling (DD) techniques. The RC drilling utilized 5.25-inch face sampling equipment, with samples collected into 60-liter bags. Samples were processed through a three-tier splitter to generate 12.5 percent representative splits for laboratory analysis, with residual material retained on-site. Diamond drilling typically commenced with HQ-diameter core before transitioning to NQ-diameter bits upon intersecting fresh rock.

The exploration program encompasses 22 drill holes totaling 9,816 meters, all completed following the June 30, 2025 reporting cutoff. The drilling focused on two primary objectives: extending the lower ore shoot downward into previously untested zones, and delineating the geometric relationship between upper and lower mineralized shoots. Infill drilling has been equally productive, with hole SGRD2487 returning 4.1 g/t Au across 11.9 meters from 499 meters depth, confirming ore continuity within the shoot linkage zone.

Analytical Protocols and Quality Assurance Framework

Fortuna maintains rigorous quality control standards across all sampling and assay procedures. All samples were transported via company vehicle or commercial courier to either ALS Global’s facility in Yamoussoukro, Côte d’Ivoire or Bureau Veritas’ laboratory in Abidjan. ALS-prepared pulps were further transported to ALS’s Ouagadougou laboratory in Burkina Faso for final analysis.

Routine gold analysis employed 50-gram fire assay charges with atomic absorption finishing. Samples exceeding 10 ppm Au were reanalyzed using 50-gram fire assay with gravimetric finishing to ensure accuracy of premium-grade intercepts. Quality control procedures incorporated systematic insertion of blanks, duplicates, and certified reference standards throughout the sample stream, complemented by internal quality control measures from both ALS Global and Bureau Veritas.

Paul Weedon, a member of the Australian Institute of Geoscientists (Membership #6001) and designated Qualified Person under National Instrument 43-101, has independently verified all data disclosed in this program, including drilling coordinates, core logging information, and analytical results.

Ongoing Resource Expansion and 2026 Exploration Outlook

The Sunbird mineralization remains demonstrably open at depth and along strike, with Fortuna’s exploration team identifying additional targets for definition in the coming months. The current drilling results extend the known mineralized system significantly beyond previous resource envelopes, suggesting a resource base capable of supporting expanded operations. With five drill rigs maintained at full capacity throughout 2026, Fortuna anticipates delivering further results that could materially enhance the Séguéla resource model.

Fortuna Mining Corp. operates three producing mines and maintains an exploration portfolio spanning Argentina, Côte d’Ivoire, Mexico, Peru, and Senegal. The company prioritizes operational efficiency, environmental stewardship, and sustainable value creation throughout its asset base. The Sunbird project represents a cornerstone long-term growth opportunity within Fortuna’s strategic mine development pipeline.