GR Silver Mining confirms mineralized extension at San Marcial, Mexico

GR Silver Mining Ltd. [TSXV: GRSL; OTCQX: GRSLF; FRANKFURT: GPE] reported that its ongoing 20,000-metre drill program at San Marcial, Mexico, continues to deliver significant drill intercepts confirming extension of mineralization beyond the 2023 NI 43-101 Mineral Resource Estimate (MRE) resource area.

Highlights: Hole SMS26-12 returned 16.1 metres true width (TW) at 162 g/t Ag, including 0.7 metres TW at 1,344 g/t Ag. Hole SMS26-14 returned 11.7 metres TW at 147 g/t Ag, including 2.85 metres TW at 429 g/t Ag.

Results from holes SMS26-12 and SMS26-14 confirm the extension of mineralized breccias for at least 300 metres to the southeast and 75 metres at depth from the 2023 MRE resource boundary.

The mineralized system of breccias is now known to extend over a total strike length of approximately 1 km and the observed mineralogical assemblage provides clear indications that mineralization may extend beyond the currently defined limits.

As our drill program progresses, future holes will test around hole SMS26-04, which returned 45.1 metres TW at 1,623 g/t Ag, including 8.25 metres at 8,579 g/t Ag as well as other nearby targets.

Results from drill holes in the SE Area Extension, particularly SMS26-12 and SMS26-14, confirm the extension of high-grade silver mineralization within chlorite–hematite hydrothermal breccias hosted at the contact between the upper Oligocene volcanic sequence and the lower Jurassic volcano-sedimentary unit.

Additional drill holes, including SMS26-09, SMS26-10, SMS26-13, and SMS26-15, confirm that the high-grade zones are strongly structurally controlled, occurring at the intersection of NE-SW structural trends with NW-SE and E-W hydrothermal breccias. Silver grades tend to decrease outside these structural intersections. This key exploration finding reinforces confidence in the geological and structural model being developed by our geological team, and its application to resource growth and drilling success as part of the ongoing 20,000-metre step-out drilling program.

GR Silver Mining’s President & CEO Eric Zaunscherb, commented, “We continue to be very pleased with the results of our 20,000-m step-out drill program at San Marcial and the efficacy of our geological model. This mineralized system is proving to be very extensive, and we are confident in seeing a significant result in our planned MRE update in the first half of 2027. The pace of the drill program has been affected by the additional distance to access the project from our new base in Durango, intermittent security issues in Sinaloa and surrounding areas, and exacerbated by the ongoing wet season. We have launched several initiatives to re-accelerate the pace, which should bear fruit in the fourth quarter.”

Zaunscherb further noted that, “The silver lining to a slower pace is that it allows us to respond to drill results as our program progresses. Future holes will test in the vicinity of hole SMS26-04 with its excellent intercept, which returned 45.1 metres TW at 1,623 g/t Ag, including 8.25 metres at 8,579 g/t Ag, as well as several other promising nearby structural targets.”

The successful intersection in drill hole SMS26-12 of 16.1 m at 162 g/t Ag, including 0.7 metres at 1,344 g/t Ag, validates the current exploration model by confirming the continuity of the mineralized zone first identified during the 2022 and 2023 step-out drilling programs.

The results also confirm the extension of the mineralized breccias for at least 300 m down-dip from surface in the SE Area. This continuity is further supported by drill hole SMS22-23, which intersected 112.6 metres at 61 g/t Ag, including 0.9 metres at 1,055 g/t Ag and drill hole SMS23-02, which returned 11.3 metres at 584 g/t Ag, including 5.5 metres at 584 g/t Ag. These results demonstrate the continued vertical extension of the high-grade silver system.

Mineralization intersected in drill hole SMS26-14 returned 11.7 metres TW grading 147 g/t Ag, including 2.85 metres TW grading 429 g/t Ag, and confirmed the lateral metres southeast of the 2023 MRE boundary. This represents a total strike length of approximately 1 km of mineralized breccia known to date.

The observed mineralogical assemblage provides clear indications that the mineralization may continue beyond the currently defined extent. Drill hole SMS26-09, located approximately 80 metres above SMS26-14, intersected a broad zone of lower-grade mineralization returning 36.0 metres grading 15 g/t Ag. This result further supports the interpretation that the mineralized system is approaching the surface, but with increasing width and grades at depth, confirms an inclined plunge of the mineralization toward the southeast. This structural interpretation will be tested by subsequent drill holes as part of the ongoing 20,000-metre step-out drilling program, with the objective of further validating and refining the current exploration model.

Highlights of 2026 step-out drilling at San Marcial: SMS26-12 intersected the typical chlorite–hematite-rich hydrothermal breccias at the contact between the upper Oligocene volcanic sequence and the lower Jurassic volcano-sedimentary sequence. The drill hole also intersected an increased presence of andesitic and dioritic dykes, which become more consistent toward the SE Extension and are interpreted as part of the subvolcanic Oligocene intrusive units in this area. Silver and lead-zinc mineralization crosscuts both dyke types, indicating that the mineralizing fluids were emplaced subsequent to, or postdated, the emplacement of the Oligocene intrusive complex; 16.1 metres TW at 162 g/t Ag from 375.05 metres down hole, including 1.3 metres at 477 g/t Ag and 0.7 metres at 1,344 g/t Ag.

SMS26-14 intersected a mineralized zone consisting of quartz–calcite–chlorite with minor hematite, occurring as hydrothermal breccia developed along the transition with the lower Jurassic volcano-sedimentary sequence. Additional stockwork veinlets were also intersected within the lower Jurassic volcano-sedimentary sequence, indicating that high-grade silver mineralization may be hosted not only along the contact zone but also within the Jurassic unit itself; 11.7 metres TW at 147 g/t Ag from 275.55 metres down hole, including 2.85 m at 429 g/t Ag.

Results from drill holes SMS26-12 and SMS2-14 confirm the extension of high-grade silver mineralization within the chlorite–hematite hydrothermal breccias and the underlying volcano-sedimentary unit in the SE Area. These results demonstrate the potential to extend the mineralized zone by at least 300 metres along strike and 75 metres down-dip beyond the limits of the 2023 MRE.

The increasing presence of subvolcanic to intrusive andesitic dykes and diorites containing silver mineralization toward the southeastern end of the SE Area supports the proposed tectonic and geological evolution model. This model suggests a closer relationship between the mineralization and an underlying intrusive body, as well as a potential transition from an epithermal to a porphyry-style mineralization system at depth.

These factors, together with the ongoing geochemical and structural vectoring studies, are key to further evaluating the potential for large-scale mineralized systems at depth beneath the San Marcial hydrothermal breccia.

The multistage hydrothermal breccias and stockwork zones are well developed in both units: the Green Volcaniclastic Unit, which hosts the chlorite-hematite hydrothermal breccias, and the Lower Jurassic Volcano-sedimentary Unit, which hosts the silicified hydrothermal breccias. These features indicate the continued circulation of epithermal fluids and the superimposition of multiple silver and polymetallic mineralizing events. This overprinting has resulted in the concentration of high-grade silver mineralization within wide, continuous, structurally-controlled breccia zones that extend both along strike and at depth.

Current drilling progress and recent encouraging results continue to support the geological model and the potential for resource growth in the San Marcial Area. An inclined plunge toward the southeast of the high-grade silver mineralization hosted within the hydrothermal breccias is being confirmed as the 20,000-metre step-out drilling program advances. The next planned drill holes will continue to test the continuity of high-grade silver mineralization at depth. The intensity of alteration, mineral assemblage, and structural indicators observed in drill holes SMS26-12 and SMS26-14 suggest that the mineralization remains open at depth, with no indication of a significant decrease in grade or mineralization intensity.

The Plomosas Project, including the recent high-grade silver discovery in the San Marcial SE Area, is emerging in 2026 as a high-grade silver district located on the southwestern edge of the Sierra Madre Occidental, at the border of Durango and Sinaloa, Mexico. The Plomosas Project, covering 7,823 ha and including the historical Plomosas underground mine, benefits from existing mine infrastructure, road access and valid permits associated with past-producing mining sites. The district contains intermediate to low-sulfidation epithermal silver and gold mineralization, hosted in hydrothermal breccias and veins. Wide, high-grade, shallow hydrothermal breccias have been delineated in the San Marcial Area, including the SE Area discovery. Step-out drilling continues in 2026, with continuous resource growth, principally targeting pure silver resources.

GR Silver Mining is Mexico-focused mineral exploration company engaged in cost-effective silver-gold resource expansion on its 100%-owned assets, located on the eastern edge of the Rosario Mining District, in the southeast of Sinaloa State, Mexico.

GR Silver Mining controls 100% of the Plomosas Project, including both the high-grade silver discovery at the San Marcial Area and the former Plomosas underground mine. Recent discoveries in the 78 km² of prospective, advanced-stage exploration concessions position the company well for resource expansion at the Plomosas Project.