Riverside Resources Reports High-Grade Gold, Silver and Base Metal Assays from Phase 2 Field Work at La Union Project

Vancouver, British Columbia–(Newsfile Corp. – May 5, 2026) – Riverside Resources Inc. (TSXV: RRI) (OTCQB: RVSDF) (FSE: 5YY0) (“Riverside” or the “Company“), is pleased to report Phase 2 field work results from the La Union Project in Sonora, Mexico. Sampling of near-surface oxidized mine workings returned very high-grade assays that reinforce drill targets ahead of the upcoming program. Detailed channel sampling and reconnaissance mapping have returned high-grade gold, silver and zinc assays at the historical Union Mine and Union Norte targets, while regional reconnaissance has defined three new target areas: Jabalí, La Negra and Ali Hill for follow-up work.

Highlights of Phase 2 Field Work

• Union Mine: 2.9 m channel sample averaging 20 g/t gold and 1.83% zinc, including 0.6 m at 91.7 g/t gold, and a 0.3 m interval grading 40% zinc.
• Union Norte: 1.0 m channel grading 4.38 g/t gold, 1,413 g/t silver, 7.7% lead and 6.38% zinc; and a separate 1.0 m channel grading 4.25 g/t gold, 1,827 g/t silver and 6.89% zinc.
• Creston: selective outcrop sampling returned 10.03 g/t gold with greater than 100 g/t silver and 8.06% lead.
• Three new target areas defined: Jabalí, La Negra and Ali Hill from regional reconnaissance carried out alongside detailed sampling
• District-wide structural and geological interpretation completed, which will be used to guide drill targeting for Phase 2 drill program scheduled for early summer 2026.

“The Phase 2 field results highlight the strong potential of the La Union district and validate our systematic approach to exploration,” said John-Mark Staude, President and CEO, Riverside Resources Inc. “The multiple ounce high-grade gold, silver and base-metal assays returned from the Union Mine and Union Norte underscore the importance of these targets as we move toward drill testing. Combined with the property-wide structural reinterpretation now in hand, our team is eager to begin the drill program with our partner Questcorp.”

Phase 2 Field Work Overview

The Riverside field team has carried out detailed underground sampling and mapping at the Union Mine and Union Norte targets in addition to reconnaissance across the broader district to identify new exploration targets. A property-wide geological and structural reinterpretation has been completed and will be incorporated into Phase 2 drill targeting. Field work continues, and additional laboratory results from samples already submitted are pending. Highlights from each target area are summarized below:

Union Mine

The historical Union Mine remains one of the project’s primary targets, with the team’s understanding of the structures controlling mineralization within and around the historic mine continuing to improve. Detailed selective and channel sampling has returned high concentrations of gold, zinc and silver, consistent with mineralization styles similar to the CRD (carbonate replacement deposit) districts like Santa Eulalia in Chihuahua and the Taylor Deposit in Arizona. The best channel sample returned a 2.9-metre interval averaging 20 g/t gold and 1.83% zinc, including 0.6 m at 91.7 g/t gold, and a 0.3-metre sample assaying 40% zinc. Channel sampling was not continuous in the underground workings but many areas showed good mineralization and target is robust for the upcoming drill program.

Table 1: Selected channel and selective assay results at Union Mine

Sample ID	Au (g/t)	Ag (g/t)	Cu (%)	Pb (%)	Zn (%)	Width (m)*
RRI-12962	91.73	11	0.07	0.29	0.4	0.6
RRI-12963	2.11	10	0.04	0.37	0.2	1.0
RRI-12964	0.056	17	0.25	0.13	40.1	0.3
RRI-12965	0.83	50	0.07	0.09	24.1	1.0

 

*Widths are true thickness as sampling was done perpendicular and on exposed material for all channel samples in this news release.

The Union Mine exploration work has focused on extending mineralization adjacent to and along strike from the historic workings. Drilling at the Union Mine will be a priority of the upcoming drill program.

Union Norte

Union Norte exhibits a similar intersection of structures to the Union Mine, with the principal structure being a 1 to 3-metre-wide breccia zone trending northwest and dipping steeply to the northeast. Low-angle veins and faults filled with mineralization create additional drill targets within the area. Systematic underground sampling, where access permitted, has returned high-grade gold, silver, lead and zinc results.

Table 2: Selected underground sample results – Union Norte

Sample ID	Au (g/t)	Ag (g/t)	Cu (%)	Pb (%)	Zn (%)	Width (m)
RRI-12927	4.379	1,413	0.75	7.7	6.38	1.0
RRI-12931	4.246	1,827	0.36	3.01	6.89	1.0
RRI-12926	1.622	817	0.34	16.4	0.82	0.8
RRI-13015	3.065	Pending	Pending	Pending	Pending	0.7
RRI-12929	1.887	366	0.04	2.01	0.35	0.5
RRI-12933	1.218	593	0.32	0.51	0.71	1.0
RRI-12932	0.44	107	0.04	1.01	9.22	0.5

 

Union Norte shows good potential for tonnage and lateral expansion and is expected to be additional area of focus of the upcoming drill program. Over-limit assays were initiated on Union Norte samples returning values greater than 100 g/t Ag; certain batches remain in progress and final over-limit values are pending.

Jabali

Jabali consists of an east-west set of interpreted low-sulfidation epithermal veins, with two main veins spaced 20-30 m apart and minor veins in between. The system is hosted in limestone-dolomite and dips to the north. Drill targets are now being outlined along the veins, with the potential that they connect to a larger feeder system at depth, representing a more significant target for additional holes at Jabali. Seven of the 13 surface samples taken returned gold values in excess of 1 g/t; 8 returned silver values in excess of 50 g/t; and 6 returned lead values in excess of 1%. The highlight results are presented below:

Table 3: 2026 Jabali Sampling Highlights from 11 Samples Received to Date

Sample ID	Au_ppm	Ag_ppm	Cu_%	Pb_%	Zn_%	Width (m)
RRI-12924	3.32	287	0.03	0.26	0.01	1
RRI-12925	37.3	980	0.30	12.7	2.37	1
RRI-12976	10.39	160	0.06	4.71	1.81	0.5
RRI-12981	28.77	88	0.02	2.94	0.13	0.3

 

Creston

At Creston, quartz veins with galena and breccia-like structures fill fault zones with strikes of 330°-345° azimuth and dips of 40° to 75° to the northeast. Phase 2 sampling has highlighted high-grade areas that will be incorporated into upcoming drill targeting.

Table 4: Selected sample results – Creston

Sample ID	Au (g/t)	Ag (g/t)*	Cu (%)	Pb (%)	Zn (%)	Width (m)
RRI-13002	10.03	>100	0.39	8.06	0.05	Oxidized fragments
RRI-13007	1.42	5	0.01	0.09	0.01	0.5
RRI-12987	0.182	356	0.03	12.8	2.62	0.3
RRI-13008	0.338	>100	0.36	5.23	1.08	1.0

 

*Batch samples are being processed for the overlimit above 100 g/t Ag. Final results will be available in the future for high silver values.

Figure 1: Location of selected high-grade gold results on La Union Project

To view an enhanced version of this graphic, please visit:
https://images.newsfilecorp.com/files/6101/295806_ccb8c9cad423d882_002full.jpg

New Target Areas – Jabalí, La Negra and Ali Hill

Field reconnaissance carried out alongside the detailed sampling at the Union Mine and Union Norte has defined three new target areas at Jabalí, La Negra and Ali Hill. Preliminary field observations are encouraging across all three areas, with mineralization styles and structural settings warranting further investigation. Additional laboratory results are pending and will be reported as data becomes available; these targets will be integrated into the broader Phase 2 work program.

Path Forward to Drilling

The results released today, together with the property-wide structural reinterpretation and the expanded aeromagnetic drone survey announced on April 1, 2026, are being integrated to refine drill hole locations for the Phase 2 drill program. With permits in hand, site access secured, and a drill contractor and geophysical service provider contracted, Riverside and Questcorp remain on track for a summer 2026 drilling campaign at the La Union Project.

Qualified Person & QA/QC

The scientific and technical data contained in this news release pertaining to the Project was reviewed and approved by Freeman Smith, P.Geo, a non-independent qualified person to Riverside Resources Inc., 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.

All widths in this news release are within 90% or more of true actual thickness as these are from exposures where sampling was done perpendicular to the trend of the mineralized unit.

Rock samples from the exploration program were shipped to ACT Labs in Zacatecas for preparation and analysis. Gold was analyzed using fire assay techniques. A 45 element ICP/EOS analysis using 4-acid digestion methods was used similar to the earlier assay work on the Project. Samples were maintained in chain of custody being delivered to the laboratory in sealed bags. Standards were inserted into the sample stream by Riverside every 20 samples and blanks inserted every 100 samples. The laboratory also inserts duplicates every 20 samples as an additional check on quality control. The QA/QC was analyzed with a check for any variations in the standards beyond 2 standard deviations and the standards passed.

About the Union Project

The Union Project is located in northwestern Sonora and shows district-scale carbonate replacement deposit (CRD) mineralization. The project hosts historical mining areas and multiple exploration targets associated with gold, silver, zinc and lead mineralization within carbonates and structurally controlled settings. Riverside operates the project through its Mexican subsidiary while advancing exploration in partnership with Questcorp.

About Riverside Resources Inc.:

Riverside is a well-funded exploration company driven by value generation and discovery. The Company has a strong balance sheet with over C$5,000,000 cash, no debt and tight share structure with a strong portfolio of gold-silver, copper, and REE assets and royalties in North America. Further information about Riverside is available on the Company’s website at www.rivres.com.

ON BEHALF OF RIVERSIDE RESOURCES INC.

“John-Mark Staude”

Dr. John-Mark Staude, President & CEO

 

Certain statements in this press release may be considered forward-looking information. These statements can be identified by the use of forward-looking terminology (e.g., “expect”,” estimates”, “intends”, “anticipates”, “believes”, “plans”). Such information involves known and unknown risks — including the availability of funds, the results of financing and exploration activities, the interpretation of exploration results and other geological data, or unanticipated costs and expenses and other risks identified by Riverside in its public securities filings that may cause actual events to differ materially from current expectations. Readers are cautioned not to place undue reliance on these forward-looking statements, which speak only as of the date of this press release.

Neither the TSX Venture Exchange nor its Regulation Services Provider (as that term is defined in the policies of the TSX Venture Exchange) accepts responsibility for the adequacy or accuracy of this release.

Source: https://www.newsfilecorp.com/release/295806/Riverside-Resources-Reports-HighGrade-Gold-Silver-and-Base-Metal-Assays-from-Phase-2-Field-Work-at-La-Union-Project