VANCOUVER, BC / ACCESS Newswire / December 22, 2025 / Rio Grande Resources Ltd. (CSE:RGR)(OTCQB:RGRLF) ("Rio Grande" or "RIO" the "Company"), is pleased to announce that it has successfully completed its 2025 geological field program at the Winston Gold-Silver Project ("Winston" or the "Project"), located in the Black Range Mountains of Sierra County, New Mexico. The field program was carried out by Dahrouge Geological Consulting USA Ltd. ("Dahrouge") (see picture 1) and included a comprehensive site visit conducted from December 2 to December 8, 2025. The program focused on detailed geological mapping, targeted surface sampling, and the compilation of historic mine workings to advance the Company's understanding of the Winston epithermal gold-silver system and to refine priority areas for follow-up exploration and drill targeting.

Jason Barnard, President and CEO of Rio Grande Resources, commented: "The completion of the 2025 field program at Winston marks an important step in advancing the Project through a systematic, data-driven approach. Dahrouge's work has confirmed the presence of a well-developed epithermal gold-silver system with multiple mineralized vein trends and clear geological indicators that support continued exploration. We are now focused on integrating this work into an updated geological model to guide the next phase of exploration and drill targeting."

Pic 1. Dahrouge Geologist Collecting Channel Sample With Rio Grande Team Member.

Exploration Highlights

• Field mapping confirmed that mineralization at Winston is hosted within a low-sulfidation epithermal gold-silver vein system, characterized by fissure-filling quartz veins and classic epithermal textures, including bladed quartz, comb quartz, colloform banding, vugs, and amethyst, indicative of boiling zones associated with precious metal deposition.

Pic 2. Sample Pictures and Descriptions

• A total of 72 samples were collected during the program, including channel and rock-chip samples, and 52 mineralized vein outcrops were mapped across the Project area (see figure 1 and pic 2).

• 58 historic mine workings including shafts, adits, pits, and trenches were identified and documented, many of which were not previously captured in modern datasets.

• Multiple mineralized vein trends and vein intersections were mapped, supporting the interpretation that Winston hosts a district-scale epithermal system with several prospective target areas rather than isolated structures.

• Several areas, including the Ivanhoe-Emporia area, Little Granite Mine area, and the Poverty Creek area of the Winston Project, were identified as priorities for follow-up work based on structural complexity, vein density, and historic development.

Figure 1. Map Of All Data Collected, Including Locations For Existing Sample

Geological Interpretation

Observations from the 2025 field program confirm that the Winston Project hosts a well-developed epithermal vein system with geological characteristics consistent with preserved precious metal mineralization. The presence of multiple vein orientations, intersecting structures, and extensive historic works suggest that mineralization is structurally controlled and may occur in stacked or plunging shoots.

Mapping results indicate that vein continuity extends for hundreds of metres to over one kilometre along strike in several areas, and that the mineralized system remains open both along strike and at depth. These findings provide a strong geological framework to guide continued exploration and drill planning.

Next Steps

The Company plans to conduct additional work including the integration of mapping and sampling results into an updated geological and structural model, evaluation of additional geophysical surveys such as magnetic, gravity, and induced polarization methods to better define structures and alteration associated with mineralization, and improved access to certain portions of the Project to support expanded sampling and mapping. This work is expected to support targeted drill planning focused on vein intersections, areas proximal to historic workings, and zones exhibiting strong epithermal vein textures. Rio Grande expects to provide further updates as additional technical work is completed and exploration plans are refined.

Qualified Person

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

Historical results referenced in this news release have not been verified by a Qualified Person and should not be relied upon as indicative of mineral resources or reserves. The Qualified Person has reviewed the sampling and mapping data disclosed herein but has not independently verified the data. Verification included a review of field procedures, sample locations, and consistency with historical records.

About Rio Grande Resources

Rio Grande Resources (CSE:RGR)(OTCQB:RGRLF) 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 100% interest in the Winston project group, which includes the 2 patented historic Ivanhoe & 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-sulfidation epithermal setting.

To view the company fact sheet and corporate presentation, please visit our website at www.riogranderesources.ca

Contact and Information

Company
Jason Barnard, President CEO and Director
(604) 767-6598
jason.barnard@riogranderesources.ca

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Forward-Looking Statements

Except for the statements of historical fact contained herein, the information presented in this news release and oral statements made from time to time by representatives of the Company are or may constitute "forward-looking statements" as such term is used in applicable United States and Canadian laws and including, without limitation, within the meaning of the Private Securities Litigation Reform Act of 1995, for which the Company claims the protection of the safe harbor for forward-looking statements. Such forward-looking statements and forward-looking information include, but are not limited to, the proposed benefits of the Arrangement. These statements relate to analyses and other information that are based on forecasts of future results, estimates of amounts not yet determinable and assumptions of management. Any other statements that express or involve discussions with respect to predictions, expectations, beliefs, plans, projections, objectives, assumptions or future events or performance (often, but not always, using words or phrases such as "expects" or "does not expect," "is expected," "anticipates" or "does not anticipate," "plans," "estimates" or "intends," or stating that certain actions, events or results "may," "could," "would," "might" or "will" be taken, occur or be achieved) are not statements of historical fact and should be viewed as forward-looking statements. Such forward-looking statements involve known and unknown risks, uncertainties and other factors which may cause the actual results, performance or achievements of the Company to be materially different from any future results, performance or achievements expressed or implied by such forward-looking statements. Such risks and other factors include, among others, the availability of capital to fund programs and the resulting dilution caused by the raising of capital through the sale of shares, continuity of agreements with third parties, the satisfaction of the conditions to the Arrangement, risks and uncertainties associated with the environment and delays in obtaining governmental approvals, permits or financing. Although the Company has attempted to identify important factors that could cause actual actions, events or results to differ materially from those described in forward-looking statements, there may be other factors that cause actions, events or results not to be as anticipated, estimated or intended. There can be no assurance that such statements will prove to be accurate as actual results and future events could differ materially from those anticipated in such statements. Although the Company believes that the expectations reflected in such forward-looking statements are based upon reasonable assumptions, it can give no assurance that its expectations will be achieved. Forward-looking information is subject to certain risks, trends and uncertainties that could cause actual results to differ materially from those projected. Many of these factors are beyond the Company's ability to control or predict. Important factors that may cause actual results to differ materially and that could impact the Company and the statements contained in this news release can be found in the Company's filings on SEDAR+. The Company assumes no obligation to update or supplement any forward-looking statements whether as a result of new information, future events or otherwise. Accordingly, readers should not place undue reliance on forward-looking statements contained in this news release and in any document referred to in this news release. This news release shall not constitute an offer to sell or the solicitation of an offer to buy securities. Please refer to the Company's most recent filings under its profile on SEDAR+ at www.sedarplus.ca for further information respecting the risks affecting the Company and its business.

The CSE has neither approved nor disapproved the contents of this news release and accepts no responsibility for the adequacy or accuracy hereof.

SOURCE: Rio Grande Resources