JR Silver Mining Limited (TSXV: GRSL; OTCC: GRSLF; DEU: GPL) Drilling results from holes SMS26-01 and SMS26-03 in the southeastern San Marcial area, Plumosas Project, Mexico, confirming continuity of high-grade silver mineralization at depths up to 500 meters from surface.
Two silver zones, including multiple intervals of high-grade silver, were intersected near the 2023 expansion drilling program, and are located on the same cross-section as SMS25-09, which returned 75.2 meters at 260 g/t silver.
SMS26-01 and SMS26-03 represent the first drill holes completed in the SE area as part of the 2026 progressive drilling program. The program is currently supported by two drilling rigs on site, with additional rigs in the pipeline to complete the planned 20,000 meters by the second half of 2026.
2026 Progressive Drilling Highlights at San Marcial: SMS26-01 intersected two distinct mineralized zones dominated by the northwest-southeast oriented San Marcial breccia intersection and northeast-oriented faults. The upper mineralized zone corresponds to an andesitic dike intersecting the upper Oligocene volcanic sequence, which was previously interpreted as barren. This high-grade silver cut opens new exploration possibilities at the top of the system, above hydrothermal breccia. The lower zone lies within a chlorite- and hematite-rich breccia, located approximately 75 m below the high-quality interval SMS25-09. It comprises a broad interval of continuous low-grade silver mineralization, indicating that the system remains open at depth: 6.45 meters at 498 g/t Ag, from 235.45 meters downhole, including 1.2 meters at 1618 g/t Ag; 61.15 meters at 15 g/t Ag from 416.45 meters downhole, including 0.7 meters at 123 g/t Ag and 0.77 g/t Au, including 0.9 meters at 171 g/t Ag and 0.85 g/t gold.
SMS26-03 confirms the continuity of high-grade silver mineralization within chlorite- and hematite-rich breccia near the contact with the Lower Jurassic volcanic sedimentary unit, located between SMS25-09 and SMS23-01, which previously intercepted 18.8 m at 145 g/t Ag. This high-grade silver intersection of multiphase hydrothermal breccia in SMS26-03 confirms the east-west extensional trend affecting the main northwest-southeast breccia trend, from surface to 500m depth: 15.6m at 351 g/t Ag, from 222.85m downhole, including 2.5m at 1395 g/t Ag.
GR Silver Mining CEO, Interim President and CEO, Eric Zaunscherb, commented: “These results reinforce our confidence in the continuity of the silver mineral system at San Marcial deep in the Southeast Zone. The successful targeting of these new high-grade intervals has been driven by our technical team’s geological work and 3D modeling and provides further support and confidence for the upcoming Mineral Resource Estimate update in the second half of 2026. Very proud of our technical team who are driving this program forward and demonstrating the significant positive potential of San Marcial.”
SMS26-01 confirms the continuity of silver mineralization within both hydrothermal chlorite and hematite breccia and overlying Oligocene units, where quartz, calcite and sulphide veins intersect the former breccia. Compared to typical refractory deposit models, boiled textures with calcite and high-grade silver (argentite and acanthite) suggest that high-grade silver mineralization should remain open at least another 100 m below the stream intersections.
SMS26-03, located between SMS23-01 and SMS25-09, is a major drill hole that helps correlate mineralization and structural trends from surface to approximately 500 metres. Compared with SMS23-01, SMS26-03 indicates that the boiling zone is well developed and preserved between approximately 300 and 600 m elevation with the potential to expand to depth, based on the results of SMS26-01.
The continuity of high-grade mineralization demonstrated by these results, coupled with geochemical modeling, advanced petrographic studies and a robust geological and structural model, provides strong confidence in the identification of a much larger thermal system with significant potential for future resource growth in the San Marcial area.
On the other hand, SMS25-13A, drilled from the same platform as SMS26-01 and SMS26-03 in the 2025 drilling program, confirms that the central zone shows an increasing tendency for lead and zinc grades. The intersection at SMS25-13A, including up to 0.65 m at 54 g/t Ag, 7.8% Pb and 0.6% Zn, helps define the potential boundaries of the boil zone, in which high-grade silver mineralization is likely as intersected at SMS25-09 and SMS26-01. In this context, SMS25-13A also supports the theory that the mineralization trends dip towards the southeast at depth.
Additional drilling rigs will begin targeting the parallel Breccia target, located approximately 300 meters from the 2023 Resource Area. This target, affected by granodiorite and diorite intrusions and hosted within volcanic sedimentary units, continues to improve the geological model, supporting the definition of a large mineralized system hosted along the edge of a regional intrusive porphyry with a suite of breccias trending northwest-southeast parallel to the main San Marcial trend that could expand the volume of the deposit. All holes were drilled from the surface.
The Plumosas Project, including the recent high-grade silver discovery in the San Marcial SE area, progresses in 2026 as an emerging high-grade silver district located on the southwestern edge of the Sierra Madre Occidental, on the border of Durango and Sinaloa, Mexico.
The Plumosas project, which covers an area of 7,823 hectares and includes the historic underground Plumosas mine, takes advantage of existing mine infrastructure, road access and permits associated with past productive mining sites. The area contains medium to low sulfidation refractory silver and gold mineralization, found in hydrothermal veins and veins. Recent exploration and drilling success has led to the identification of extensive, high-quality, shallow hydrothermal zones in the San Marcial area, including the SE Zone discovery, where progressive drilling is underway in 2026, with the goal of continued resource growth.
Regarding the historic Plumosas Mine, an underground mine operated by the Mexico Group from 1985 to 2000, work is ongoing to support future decisions regarding the implementation of a bulk sampling test mining programme.
JR Silver Mining is a Mexico-focused mineral exploration company engaged in the cost-effective expansion of silver and gold resources on its 100% owned assets, located on the eastern edge of the Rosario Mining District, in the southeastern state of Sinaloa, Mexico.
GR Silver Mining controls 100% of the Plumosas project, including the former Plumosas underground mine and extensive areas of high-grade silver minerals in the San Marcial area. Recent discoveries at 78 km2 The advanced and highly prospective exploration concessions position the Company well for resource expansion at the Plumosas Project.
