Dr. John-Mark Staude reports

RIVERSIDE RESOURCES AND QUESTCORP ANNOUNCE COMMENCEMENT OF DRILLING AT UNION PROJECT, SONORA, MEXICO

Riverside Resources Inc. has commenced drilling at the La Union project in northwestern Sonora, Mexico. This work is being carried out in partnership with Questcorp Mining Inc., which is earning into the project through an option agreement from Riverside (see press release dated May 6, 2025).

Highlights:

• Initial drill program is designed to expand known zones of mineralization, test new targets and explore areas surrounding multiple historical mine workings within the 25-square-kilometre project area;
• Drill program will consist of more than 1,500 metres of diamond core drilling across six holes, each averaging 250 metres in depth;
• Drilling to test the carbonate-hosted replacement deposit (CRD) style of mineralization, with gold associated with mantos, chimneys and along structural zones;
• Angled drill holes are aimed at cutting perpendicular to stratigraphic targets and some structural targets, which is typical in CRD systems;
• Structural features may have served as mineralizing conduits and are key targets in the current drill program.

The recent exploration work over the past three months by Riverside has improved the understanding of the structural geology and stratigraphy in the Sierra El Viejo, the mountain range immediately to the west of the La Union project. The La Union district lies along the flanks of this range, where these updated interpretations help guide current exploration efforts. The exploration target focus is for a large potential gold discovery that expands from previous smaller-scale mine operations on the property. The drill program will begin to test the new concepts and expand past previous mining.

Dr. John-Mark Staude, chief executive officer of Riverside Resources, stated: "We are pleased to move forward with initial drilling, which will include one or two holes in each area to begin evaluating the CRD target concepts and potential extensions beyond the limits of historical mining. Ideally, this focused initial program will be followed by a more robust drilling campaign to significantly expand on early results. CRD systems typically require multiple rounds of drilling to identify the most prospective zones, so we're pleased to be getting started now. Riverside has a strong portfolio of over seven projects in Mexico, and it's exciting to see this project advancing with partner-funded drilling. Over the next two quarters, we're hopeful that additional districts within our portfolio will also move toward drill testing."

The drill program targets include more than four different areas, beginning with this early-stage stratigraphic and orientation phase of drilling exploration aimed at evaluating the scale of alteration and indications of a mineralized system. This will be the first drilling ever conducted on most of the targets, despite past mining having occurred in the majority of these areas. The initial program will consist of one to three holes per area, primarily for orientation purposes. Follow-up drilling is planned and can be expanded based on initial results, which will help verify the stratigraphy, lithologies and structural features allowing for improved modelling and next-stage discovery targeting. The four areas are listed below:

• Union main mine area: The program will use angled drill holes to test limestone and other carbonate stratigraphic hosts within the Clemente formation, with the potential to reach the underlying Caborca formation. These units are considered the primary hosts for replacement-style mineralization.
• North Union mine area: The initial focus of the program will be on testing structural interpretations. Additional drilling is anticipated following this first phase as results will help guide future drill testing of areas with past mining activity and various structural orientations.
• Cobre mine area: The Clemente formation is the primary host unit, and structural features combined with areas of past mining provide multiple target zones. Drilling will begin with an initial stratigraphic test hole to help orient around the thickness of the host unit and extend into the lower Caborca formation, which is also a favourable host for CRD-style mineralization.
• Central Union area: Structural targets, as possible mineralization feeder zones, are a key focus in this past mining manto area. There are extensive additional target zones in the area, and this initial orientation drilling will provide vectoring for the next stage of drilling and further study of the Clemente formation and possibly into the Caborca formation as currently interpreted.

General overview of the La Union project

The project is summarized in a recently published National Instrument 43-101 technical report available under Questcorp's SEDAR+ profile. Riverside initially acquired the project and subsequently consolidated additional inlier mineral claims, building a strong land position. Riverside then advanced the project through surface access agreements and drill permitting, making it a turnkey exploration opportunity for Questcorp.

The project was originally identified through Riverside's exploration work in the western Sonora gold belt, conducted in collaboration with AngloGold Ashanti Ltd., Centerra Gold Inc. and Hochschild Mining PLC. Earlier research by Riverside founder Dr. John-Mark Staude also contributed to recognizing the district's potential. Initial work by members of the Riverside team, drawing on more than two decades of geological compilation and analysis, further confirmed the region as highly prospective.

At the project, historical mining by the Penoles Mining Company targeted chimney- and manto-style replacement bodies within the upper oxide zones. As a result, the underlying sulphide zones represent immediate and compelling drill targets for further exploration.

The project features favourable limestone host rocks, an extensive alteration footprint and multiple small-scale historical workings, with mineralization styles similar to those at the Hermosa project in southern Arizona. At Hermosa, South32 is advancing mine development following its acquisition of the project from Arizona Mining. On Feb. 15, 2024, South32's board approved a $2.16-billion (U.S.) capital investment to develop the Taylor zinc-lead-silver deposit, representing the largest private mining investment in southern Arizona's history. The project is now considered one of the most significant undeveloped base metal assets in the United States.

At the La Union project, immediate drill targets offer the potential for significant-scale discoveries. La Union is well positioned for near-term exploration success, with targets that include both oxide and deeper sulphide mineralization.

Overview of the option agreement

On May 5, 2025, Riverside's wholly owned subsidiary, RRM Exploracion SAPI de CV (the vendor), entered into a definitive option agreement with Questcorp (the optionee) for the La Union project. As part of the agreement, Questcorp issued shares to Riverside, making Riverside a 9.9-per-cent shareholder and aligning both parties' interests in the project's success. With financing provided by Questcorp, an initial $1-million exploration program is now under way. This marks the first phase of a larger, $5.5-million work commitment, contingent on exploration results and Questcorp's continued participation.

Qualified person and quality assurance/quality control

The scientific and technical data contained in this news release pertaining to the project were reviewed and approved by Freeman Smith, PGeo, a non-independent qualified person to Riverside Resources, who is responsible for ensuring that the information provided in this news release is accurate and who acts as a qualified person under National Instrument 43-101, Standards of Disclosure for Mineral Projects.

Rock samples from previous exploration programs discussed above at the project were taken to the Bureau Veritas Laboratories in Hermosillo, Mexico, for fire assaying for gold. The rejects remained with Bureau Veritas in Mexico while the pulps were transported to Bureau Veritas's laboratory in Vancouver, B.C., Canada, for 45-element ICP/ES-MS analysis using four-acid digestion methods. A QA/QC program was implemented as part of the sampling procedures for the exploration program. Standards were randomly inserted into the sample stream prior to being sent to the laboratory.

About Riverside Resources Inc.

Riverside is a well-financed exploration company driven by value generation and discovery. The company has a solid balance sheet with no debt and less than 75 million shares outstanding with a strong portfolio of gold-silver and copper assets and royalties in North America. Riverside has extensive experience and knowledge operating in Mexico and Canada and leverages its large database to generate a portfolio of prospective mineral properties. Riverside has properties available for option, with information available on the company's website.

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