GR Silver Sees Pilot Mining Program Supporting Permitting Pathway in Mexico

• GR Silver Mining is evaluating a 60-200 tonnes per day pilot plant and bulk sample test mining (BSTM) program at the permitted Plomosas mine, with 7.4 kilometres of accessible underground development.
• Plomosas holds a mining concession while San Marcial holds an exploration concession; demonstrating operational competence at Plomosas could shorten San Marcial's 5-7 year permitting timeline.
• 20,000 metre drill program at San Marcial targeting depth extension and parallel breccia structures within 134 million ounce silver equivalent resource; recent intercepts include 6.45 metres at 498 grams per tonne silver and 15.6 metres at 351 grams per tonne silver.
• The geological model indicates an intrusive-related porphyry system with drilling testing 20% of the perimeter to date; one rig is dedicated to the first parallel breccia structure.
• Mineral resource estimate (MRE) update targeted for the second half of 2026 following drill program completion; the company holds C$28.5 million cash as of May 1, 2026, with no debt

Bulk Sample Program Targets Permitting Pathway 

GR Silver Mining (TSX.V: GRSL | OTCQX: GRSLF | FRA: GPE) is evaluating a pilot plant and bulk sample test mining (BSTM) program at its Plomosas project in Sinaloa, Mexico, a development targeting operational continuity between exploration and production permitting timelines. The company is working on engineering for purchasing a pilot plant in the range of 60 to 200 tonnes per day, with the BSTM program designed to demonstrate operational capacity to Mexican regulators while permitting work at the San Marcial resource area advances from exploration to production status. The distinction between mining concessions and exploration concessions in Mexico creates a sequential pathway in which demonstrating operational competence at the permitted Plomosas mine could support a shorter permitting timeline for advancing San Marcial.

Pilot Plant & Permitting Infrastructure

The Plomosas mine holds a mining concession with existing permits in place, alongside 7.4 kilometres of underground development already accessible for bulk sampling. The Plomosas mine operated until 2001, when Grupo Mexico completed its program and removed the mill from the site. No processing facility currently exists onsite. The company is assessing plant options for installation at Plomosas to commence the BSTM program.

Interim President and Chief Executive Officer of GR Silver Mining, Eric Zaunscherb, explained the permitting rationale for the pilot plant program in relation to the company's broader development timeline:

"While Plomosas is a mining concession, San Marcial, however, is an exploration concession. So, in today's environment, to permit that and get that into a producing state, going through all the technical studies and permitting process, that could be 5 to 7 years. However, if we proceed with the bulk sample test mining program at Plomosas and demonstrate to the regulators that we're doing a good job there, we're employing people there, then there's an opportunity to make that process for permitting and technical studies for San Marcial shorter."

Drilling & Resource Expansion

GR Silver Mining is conducting a 20,000 metre drill program at the San Marcial resource area, which forms part of the company's 134 million ounce silver equivalent resource established in the 2023 mineral resource estimate (MRE). The program targets continuity and depth extension along the main breccia body to the southeast, as well as testing parallel breccia structures identified closer to an intrusive body interpreted to be part of a porphyry system.

The first two holes released from the current program intersected 6.45 metres at 498 grams per tonne silver from 235.45 metres downhole, including 1.2 metres at 1,618 grams per tonne silver, and 15.6 metres at 351 grams per tonne silver from 222.85 metres downhole, including 2.5 metres at 1,395 grams per tonne silver. 

Zaunscherb discussed the depth continuity demonstrated by the drilling program:

"We're showing continuity to roughly 500 metres depth in the main southeast extension.”

The company is currently drilling holes 10, 11, and 12 of the program, with three rigs onsite. The average resource thickness at San Marcial is 22 metres, contributing to efficient ounce additions during exploration.

Geological Model & Exploration Targets

The geological interpretation at San Marcial involves an intrusive-related mineralised system in which the main silver-bearing breccia body occurs along northwest-trending faults on the shoulder of an intrusive body. Drilling to date has tested approximately 20% of the perimeter around this intrusion. Parallel breccia structures identified closer to the intrusive body show elevated gold contribution, while surface sampling has identified copper and molybdenum enrichment toward the centre of the intrusive body.

Zaunscherb described the emerging geological model and its exploration implications:

"There's a porphyry model that one can start speaking of here. Porphyry model in the middle, parallel breccias as you come out, and then you see that breccia that we had San Marcial discovery originally was aimed upon.”

One drill rig is currently dedicated to testing the first parallel breccia structure, with deeper holes planned into the intrusive body later in the program. Vice President of Exploration, Luis Soto, leads the geological team.

Metallurgical Work & Technical Studies

Metallurgical testing is underway to evaluate leaching processes and the potential for producing doré onsite. The company plans to commission a preliminary economic assessment (PEA) that will evaluate a development sequence starting with the Plomosas mine and incorporating San Marcial as a complementary project. An MRE update is targeted for the second half of 2026, following completion of the drill program, with a PEA to be commissioned thereafter.

Operations & Infrastructure in Durango

GR Silver Mining has established its logistical base, core shack, and exploration office in Durango City, Durango. The Plomosas property is located in Sinaloa, with road access from Durango covering the majority of the route. The company began this operational pivot in November of the prior year. Road upgrades are in progress to support the addition of a fourth and fifth drill rig to the program. Country Manager Cacho Molina manages regulatory engagement and operational coordination in Mexico.

Near-Term Catalysts

Near-term catalysts include additional drill results from the ongoing program, a resource update in the second half of 2026, commissioning of the PEA, and a potential decision on pilot plant purchase and installation. The company reported cash of C$28.5 million as of May 1, 2026, with no debt.

Zaunscherb emphasised operational continuity under the company's interim leadership structure:

"We continue to drill. We continue to move forward with our program.”

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