Plomosas Mine Area

Past-producing, permitted silver mine with infrastructure and exploration upside in the southwestern edge of the Sierra Madre Occidental (“SMO”), Rosario Mining District, Sinaloa, Mexico.

View NI 43-101 Reports

Geologists-at-the-plomosas-underground-mine

Resource Growth and Development

The Plomosas Mine Area includes a past-producing underground silver–gold–lead–zinc mine, operated by Grupo Mexico S.A. de C.V., from 1985 until 2001. Recent drilling and current bulk sampling studies aim to define key parameters for the potential installation of new processing operations on site.

Existing permits and authorizations, along with infrastructure such as roads, a camp, and access to power and water, place the Plomosas Mine in a strong position for renewed development.

Recent geological modelling combined with historical production data highlights strong potential for resource expansion.

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 the current Indicated and Inferred resources across these areas.

The resources 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 (198 km by road), at the southwestern end of the 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 a Pb-Zn-rich epithermal hydrothermal breccia hosted within a low-angle fault, and is recognized over more than 1 km of its north-south oriented 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:

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.
Galena–sphalerite event (Pb-Zn rich): chalcopyrite, sphalerite, galena, quartz-chlorite-carbonate.

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. The presence of infrastructure and permits assist in the future development of both areas.

Learn more about the San Marcial Area