Drilling & Parallel Discovery Strategy Position GR Silver Mining for Resource Expansion at San Marcial

• Approximately 80% of San Marcial's chargeability anomaly remains untested, and parallel silver-bearing structures represent potential sources of resource expansion beyond the current 134 million-ounce silver equivalent base.
• Step-out drilling is underway with a 20,000-meter program aimed at extending the deposit and testing undrilled geophysical anomalies.
• The 2025 exploration campaign delivered a 75-meter intercept grading 260 grams per tonne of silver, backed by C$34 million in financing and a five-year drilling permit.
• The nearby Plomosas past-producing mine provides existing underground access, power infrastructure, surface facilities, and permits that may reduce capital requirements relative to a greenfield development.
• Upcoming catalysts include the Mineral Resource Estimate in the second half of 2026 and the maiden Preliminary Economic Assessment that will give investors the first consolidated view of the district’s scale, economics, and growth potential.

Exploration Mobilisation at San Marcial

GR Silver Mining (TSXV: GRSL | OTCQX: GRSLF | FRA: GPE) has initiated a 20,000-meter step-out drilling program at the San Marcial project in Sinaloa, Mexico, targeting extensions of the existing mineral resource and previously identified geophysical anomalies. Approximately 80% of the chargeability anomaly footprint remains undrilled, suggesting that current drilling has tested only a fraction of the mineralised system.

President & Chief Executive Officer of GR Silver Mining, Marcio Fonseca, outlined the exploration rationale:

"We are targeting the step out drilling that's the edges of the resource as an expansion with resource growth, but also we have a discovery, a second one parallel branches, that's a new discovery which can add ounces of silver as well for a pure silver area.”

The mobilisation follows a 2025 exploration year in which the company raised C$34 million, secured a five-year drilling permit, and reported an intercept of 75 metres grading 260 grams per tonne of silver (293 grams per tonne silver equivalent). Development work is also advancing at the Plomosas mine, located approximately 5 kilometres from San Marcial, supporting the company’s broader plan to build a district-scale silver development platform in Mexico.

Structure, Scope & District Context of the Drill Campaign

The San Marcial drill campaign is primarily designed as a step-out program rather than infill drilling aimed at upgrading resource classifications. Step-out drilling targets the edges of known mineralisation to determine whether the deposit forms part of a larger mineralised system. GR Silver Mining reported a consolidated Mineral Resource Estimate (MRE) of 134 million ounces of silver equivalent across the San Marcial and Plomosas areas in 2023, and the current program is focused on testing whether additional structures could extend that footprint.

Management has identified additional exploration targets around the existing deposit. Several parallel silver-bearing structures have been identified alongside the main resource, following the same geological system that formed the current mineralisation, while geophysical surveys have also highlighted multiple undrilled anomalies that may indicate additional sulphide mineralisation. The campaign builds on the geological framework established during 2025, when drilling confirmed near-surface, wide-interval mineralisation along the San Marcial trend and suggested the hydrothermal system could extend laterally and at depth into currently untested areas.

Fonseca referenced the 2025 results, including the C$34 million raised during that period, as validation of the company's exploration methodology:

“2026 is going to be a transformational year with the support of everything that we have done in 2025. When we came to the market and raised $34 million, we told the market that we are going to be granted a long-term permit, we were granted a five-year drilling permit, and we said that we are going to continue to hit discoveries, we hit 75 metres at 260 grams per tonne.” 

Drilling is now testing whether these parallel structures and undrilled geophysical anomalies represent additional discovery zones capable of expanding the existing resource and supporting the development of a larger district-scale silver system.

Plomosas Mine & Development Infrastructure

While exploration advances at San Marcial, development work is progressing at the Plomosas mine, a past-producing underground silver-lead-zinc operation whose existing infrastructure, permitting frameworks, and operational logistics support an integrated project plan.

Metallurgical test work and engineering for a pilot plant supporting bulk sample test mining (BSTM) have been completed, with the exact installation location expected to be confirmed in the coming months. Existing underground development, power access, and surface facilities at Plomosas support the BSTM program, which is intended to validate metallurgical assumptions used in economic models and generate operational data ahead of potential commercial production.

Toward an Integrated Economic Model

Exploration and development at San Marcial and Plomosas are advancing toward an integrated MRE update and a maiden Preliminary Economic Assessment (PEA) expected in the second half of 2026. The study will evaluate both assets as components of a combined mining operation reflecting their operational and logistical linkages. Integrating the projects allows the development strategy to leverage shared infrastructure and gain advantages.

Fonseca described how this infrastructure advantage is expected to shape the PEA:

"From the PEA, investors should expect a mining project that will not have a really big capex because the Plomosas area is going to bring all the infrastructure in place, like power lines, buildings, and other facilities, plus the permits, and it's 5 kilometres only from San Marcial.  We're looking to have a sizable project that is going to be really well placed for the future demand of silver in Mexico or worldwide.”

The distinction is relevant to the project's commercial profile. San Marcial is structured as a potential silver-dominant project, while Plomosas is oriented toward producing a polymetallic concentrate. Developing the two assets within a single economic framework would incorporate both product types into a combined operational plan, a distinction the upcoming PEA is expected to reflect.

The combined project benefits from existing infrastructure and permits at Plomosas, which can lower upfront capital expenditure (capex) and potentially improve internal rate of return (IRR) while reducing financing requirements. The second half of 2026 MRE update and PEA will provide the first opportunity for investors to evaluate the district’s combined net present value (NPV) and IRR under a single economic framework.

The Investment Thesis for GR Silver Mining

• Exposure to district-scale resource growth potential, with approximately 80% of the San Marcial chargeability anomaly untested and newly identified parallel silver-bearing structures providing potential to expand the existing 134 million-ounce silver equivalent resource base.
• A 20,000-meter step-out drilling program targeting extensions of the current deposit and undrilled geophysical anomalies, designed to test if San Marcial is part of a larger mineralised system.
• The 2025 exploration campaign delivered a 75-metre intercept grading 260 grams per tonne of silver, C$34 million in financing, and a five-year drilling permit, providing the operational and financial foundation for the current step-out program.
• Infrastructure-supported development potential through the nearby Plomosas past-producing mine, where existing underground development, power access, permits, and surface facilities may reduce capital expenditure (capex) relative to a greenfield development.
• The upcoming integrated Mineral Resource Estimate update and maiden Preliminary Economic Assessment will provide the first consolidated assessment of net present value and internal rate of return for the San Marcial-Plomosas district, giving investors insight into project scale, profitability, and growth prospects.

The combination of an active step-out drill program, infrastructure-supported development at Plomosas and a maiden Preliminary Economic Assessment on the horizon defines the investment case at its current stage. As drilling results emerge and the integrated economic study takes shape through the second half of 2026, investors will have a progressively clearer basis for evaluating the district's scale, capital requirements, and long-term production potential.

TL;DR

GR Silver Mining is advancing its San Marcial project with a 20,000-meter step-out drilling program targeting extensions of the existing 134 million-ounce silver-equivalent resource and undrilled geophysical anomalies, including newly discovered parallel silver-bearing structures, building on a 2025 campaign that delivered a 75-metre intercept grading 260 grams per tonne of silver. The nearby Plomosas past-producing mine provides existing infrastructure, permits, and facilities that could reduce development costs and accelerate production. Upcoming catalysts include an integrated 2026 MRE and maiden PEA, which will give investors the first consolidated view of the district’s scale, economics, and growth potential, with results expected to inform whether the district can support a larger, integrated development scenario.

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