Mr. Jason Barnard reports

RIO GRANDE RESOURCES ADVANCES DISTRICT-SCALE GOLD-SILVER TARGET DEFINITION AT ITS WINSTON PROJECT THROUGH STRUCTURAL MAPPING OF MULTIPLE VEIN CORRIDOR SYSTEMS

Rio Grande Resources Ltd. has completed its phase 2 field sampling and structural mapping program at the Winston gold-silver project, located in the Black Range Mountains of Sierra county, New Mexico. The program was completed by Dahrouge Geological Consulting USA Ltd., and included extensive structural mapping and surface sampling designed to refine the company's geological understanding of mineralized vein trends across the property ahead of its planned phase 1 drill program.

During the seven-day program conducted the second week of May, 2026 (see news release dated May 6, 2026), Dahrouge collected 75 rock chip samples and five channel samples, representing an additional 16 individual samples, for a total of 91 individual samples submitted for analysis. The program's extensive structural mapping, represented by 307 new data points, has significantly enhanced the company's understanding of mineralized vein trends and interpreted corridors throughout the Winston claim block. The structural data set, which includes mapped vein orientations, mineralization characteristics, textural observations and structural measurements, is expected to play an important role in refining and prioritizing drill targets for the company's planned phase 1 drill program.

Highlights include:

• 91 individual samples collected, including rock chip and channel samples;
• 307 new structural data points collected across multiple target areas;
• Multiple steeply dipping vein corridors and structural intersections identified;
• Mapping supports continuity of interpreted mineralized trends between Poverty Creek, Highway 59, Ivanhoe-Emporia and Little Granite;
• Epithermal quartz textures observed across several target areas, including bladed quartz, drusy quartz, comb quartz, amethyst, colloform banding and vuggy textures.

Jason Barnard, chief executive officer of Rio Grande Resources, commented: "This second phase field program has significantly advanced our understanding of the Winston project and further strengthened our confidence in the scale of the mineralized system. The structural data collected by Dahrouge has helped identify and refine several priority target corridors that we believe have strong potential. We are particularly encouraged by the increasing evidence that Winston may represent a larger district-scale epithermal system and look forward to integrating the pending assay results into our evolving drill targeting model in advance of our planned phase 1 drill program, as we continue advancing the Winston project for the benefit of our company and its shareholders."

The company believes the completed field program has materially advanced its geological model for the Winston project. Multiple vein corridors appear to extend through key target areas, including Poverty Creek, north of Highway 59, Ivanhoe-Emporia and the Little Granite area. The recognition of these potential continuities, combined with the newly collected structural data set, is expected to help refine targets where future drilling may test for vein intersections, continuity along strike and mineralization at depth.

District-scale potential further supported

Mapping completed to date increasingly supports the interpretation that Winston may represent a connected, district-scale low-sulphidation epithermal gold-silver system rather than a series of isolated vein occurrences. Multiple steeply dipping vein corridors, including vein swarms with several structural intersection points, were identified in this program. In low-sulphidation epithermal systems, these structural intersections can represent favourable zones for enhanced hydrothermal fluid flow, a key geological process associated with precious metal deposition.

Throughout the property, textures typical of a low-sulphidation epithermal system, including bladed quartz, drusy quartz, comb quartz, amethyst, colloform banding and vuggy textures, were identified within structurally controlled vein systems. These observations are consistent with the geological characteristics identified during the company's December, 2025, field program and further support the interpretation of a large-scale epithermal gold-silver system at Winston (see news release dated Dec. 12, 2025).

In the Poverty Creek region, mapping identified a broad swarm of structurally controlled veins extending from the northern portion of the claim block through Highway 59 and into the Poverty Creek corridor. Several of these vein trends appear continuous across multiple target areas and are associated with historical workings and previously identified mineralized structures.

Structural measurements collected during the program also improved the company's understanding of vein orientations and controls on mineralization within the Ivanhoe-Emporia region.

Next steps

Assay results from the completed sampling program are currently pending. Upon receipt, the company plans to integrate the assay results with the newly collected structural mapping data, previously reported surface sampling results and airborne geophysical interpretations to refine and prioritize high-confidence drill targets ahead of the planned phase 1 drill program.

The company expects this integrated data set to support drill targeting focused on structurally favourable areas, including vein intersections, interpreted mineralized corridors, and zones demonstrating strong epithermal textures and structural continuity across the Winston project.

Corporate secretary appointment

Rio Grande Resources is also pleased to announce the appointment of Andrew Brown as corporate secretary, effective May 25, 2026. Mr. Brown has over 13 years of experience in the public markets, and has served as an executive officer of both TSX Venture Exchange- and Canadian Securities Exchange-listed issuers. Mr. Brown is the founder of Ardent Corporate Services Inc. and has served as president of a Vancouver-based corporate services firm. He previously served as vice-president, corporate affairs, and corporate secretary of a TSX Venture Exchange-listed issuer. His areas of specialization include business development, corporate governance, executive management, project management and public company administration. Rio looks forward to benefiting from Mr. Brown's extensive experience and leadership as he assumes the role.

Qualified person

The scientific and technical information contained in this news release has been reviewed and approved by Jacob Anderson CPG, MAusIMM, a qualified person as defined under National Instrument 43-101. Mr. Anderson is independent of Rio Grande Resources.

The qualified person has reviewed the sampling procedures, analytical methods and results disclosed herein, and is satisfied that the information has been accurately presented. Verification included a review of field procedures, sample locations and consistency with historical records.

About Rio Grande Resources Ltd.

Rio Grande Resources is a burgeoning mineral exploration company focused on unlocking the high-grade gold and silver potential within its 3,000-acre drill-ready property in the Black Range of Sierra county, New Mexico. The company holds a 100-per-cent interest in the Winston project group, which includes the two patented historic Ivanhoe and Emporia claims, and Little Granite mines, all known for their past production of high-grade precious metals. Rio Grande Resources is led by a team of experienced professionals with expertise in mineral exploration and development, who are targeting large-scale precious metal discoveries within the property's well-documented low-sulphidation epithermal setting.

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