Plomosas Mine Area

A past-producing, fully permitted silver mine with infrastructure and exploration upside in the Rosario Mining District.

View NI 43 101 Reports

Geologists-at-the-plomosas-underground-mine

Resource Growth and Development

The Plomosas Mine Area is located within 5 kilometres of the San Marcial Area in the Rosario Mining District, Sinaloa, Mexico. Together, these properties provide GR Silver Mining with control over 9,764 hectares, covering most of the silver–gold–lead–zinc (Ag-Au-Pb-Zn) mineralized zones in the district.

The Plomosas Mine Area includes a past-producing underground silver–gold–lead–zinc mine, historically operated by Grupo Mexico S.A. de C.V., within 8,515 hectares of concessions. With existing permits and authorizations for future operations, and infrastructure such as a 100-person camp and access to power and water, the site is well positioned for renewed development.

Recent geological modelling combined with historical production data highlights strong upside potential for resource expansion, exploration, and new discoveries.

Photo caption and technical notes

Numbers are rounded
* AgEq = calculated from the metal prices and recoveries using the equation AgEq = ((Ag grade x Ag Price x Ag recovery) + (Au grade x Au price x Au recovery) + (Pb grade x Pb price x Pb recovery) + (Zn grade x Zn price x Zn recovery) + (Cu grade x Cu price x Cu recovery))/(Ag price x Ag recovery)
(1) Mineral Resources which are not Mineral Reserves, do not have demonstrated economic viability
(2) The estimate of Mineral Resources may be materially affected by environmental, permitting, legal, title, taxation, socio-political, marketing, or other relevant issues
(3) The Inferred Mineral Resource in this estimate has a lower level of confidence than that applied to an Indicated Mineral Resource and must not be converted to a Mineral Reserve. It is reasonably expected that the majority of the Inferred Mineral Resource could be upgraded to an Indicated Mineral Resource with continued exploration
(4) The Mineral Resources were estimated using the Canadian Institute of Mining, Metallurgy and Petroleum (CIM), CIM Standards on Mineral Resources and Reserves, Definitions and Guidelines prepared by the CIM Standing Committee on Reserve Definitions and adopted by the CIM Council

NI 43-101 Resource Estimate

In March 2023, GR Silver Mining announced an updated NI 43-101 mineral resource estimate for the Plomosas Project, which incorporates the San Marcial, Plomosas Mine, and San Juan-La Colorada Areas. The summary table below outlines current indicated and inferred resources across these areas.

The San Marcial and Plomosas deposits remain open along strike and at depth, offering significant exploration potential. Full details are available in the 2023 Technical Report.

NI 43-101 Reports

Royalty Interests

The following royalty interests and purchase rights apply to the Plomosas Property:

2% NSR to Royalty Streaming Mexico S.A. de C.V., with a buyback right of 1% for US$1.0M.
1.75% – 3.5% net production and sales royalty to Industrial Minera México (a Grupo Mexico subsidiary), based on the price of zinc.

Plomosas Mine Area Geology

The Plomosas Property lies 98 km southeast of Mazatlán in a straight line (198 km by road), at the southwestern end of the Sierra Madre Occidental (SMO). It is situated within an erosional window typical of the SMO, shaped by regional extensional events.

Basement rocks: Late Jurassic volcaniclastic units and felsic intrusions (164–151 Ma).
Oligocene volcanic sequence: Silicic ignimbrites, lava flows, and basaltic flows, intruded by diorite porphyries (32–28 Ma early phase; 28–26 Ma late phase).
Younger intrusions: Miocene rhyolitic domes.

Mineralization

The Plomosas deposit is hosted in a low-angle fault, Pb-Zn rich epithermal hydrothermal breccia, recognized over more than 1 km strike length and dipping 45°–60°W. The main mineralized zone has been traced for 150 m along strike and 700 m down dip.

Recent drilling and modelling have identified three mineralization events:

Galena–sphalerite event (Pb-Zn rich): chalcopyrite, sphalerite, galena, quartz-chlorite-carbonate.
High-grade silver event: chalcopyrite, bornite–covellite–pyrite–jalpaite with quartz–chlorite–epidote–amphibole.
Low sulphidation gold veining: electrum with quartz veinlets, calcite fractures, pervasive silicification, sericitization, and disseminated pyrite.

Connected Growth with San Marcial

Together with the nearby San Marcial Area, the Plomosas Mine Area strengthens GR Silver Mining’s control of nearly 10,000 hectares in the Rosario Mining District.

Learn more about the San Marcial Area

Connected Growth with San Marcial

Together with the nearby San Marcial Area, the Plomosas Mine Area strengthens GR Silver Mining’s control of nearly 10,000 hectares in the Rosario Mining District.

Learn more about San Marcial Geology and Mineralization