San Marcial Area

San Marcial Area Summary

VRIFY Tour of San Marcial and Plomosas Mine Areas

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The San Marcial Area (“San Marcial Property”) contains a significant silver resource, illustrating the potential for future open pit and underground development, in addition to high-grade gold mineralization discovered in recent drilling. The potential of the San Marcial Property was enhanced by a new discovery of silver mineralization at the SE Area in August 2022. The 1,250-hectare property is located 98 kilometres southeast of Mazatlán, in the state of Sinaloa, and 5 kilometres south of the Company’s Plomosas Mine Area.

In March 2023, GR Silver announced an updated NI 43-101 mineral resource estimate for the Plomosas Project, incorporating the San Marcial, Plomosas Mine and San Juan-La Colorada Areas. Full details are contained in the 2023 Technical Report.

See News Release dated May 4, 2023.
Numbers are rounded
* AgEq is calculated from the metal prices and recoveries using the equation AgEq = ((Au grade*Au price*Au Recovery) + (Ag grade*Ag Price*Ag Recovery) + (Pb grade*Pb Price*Pb Recovery) + (Cu grade*Cu Price*Cu Recovery) + (Zn grade*Zn Price*Zn Recovery)) / (Ag Price*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

The San Marcial deposit remains open along strike and at depth. The following royalty interest and purchase rights are related to the San Marcial property: 0.75% NSR to EMX Royalty Corporation, with the ability to purchase back in full for US$1.25M and 3.0% net production royalty to Industrial Met-Sin, with the opportunity to purchase back in full or part for US$0.6M per each 1%.


The San Marcial prospects lie at the intersection of a major crustal east-west structure with north-northwest trending structures within the Rosario Mining District, located on the western edge of the Sierra Madre Occidental. The geology at San Marcial can be sub-divided into two distinct underlying rock types. The Upper Volcanic Group of basal conglomerates, rhyolites and dacites occurring in the higher and more mountainous portions of the Project. This unit lies on the erosional surface above the Lower Volcanic Group. The Lower Volcanic Group consists of an epiclastic sequence of lapilli tuffs and volcanic ash, with intercalated dacites and trachyandesites. The known silver prospects at San Marcial are hosted along what appears to be a narrow set of northwest trending fault structures with a 60° northeast dip, near the prospective unconformity. The San Marcial resource area hosts a low sulphidation epithermal system, rich in silver and gold.


The area displays low sulphidation epithermal systems rich in silver.

Several different styles of mineralization have been identified at the San Marcial Area including two main types of breccia hosting Ag and Au mineralization:

— Hematitic hydrothermal breccia: hematite + calcite + quartz

— Siliceous hydrothermal breccia: chlorite + quartz + pyrite

The resource area is dominated by the low sulphidation epithermal style environment described above, and the two styles of associated hydrothermal breccia. The San Marcial breccia-hosted deposit is strongly associated with a northwest-southeast oriented structural trend, and possibly affected by other cross cutting structural features. While San Marcial is considered a silver deposit, the multi-phase mineralization creates a multi-commodity deposit with zinc and lead closely associated with the silver.

In addition to the breccia and fault hosted mineralization at San Marcial, there are zones of vein and stockwork mineralization, generally peripheral to the breccia-hosting silver mineralization.

Recent exploration by GR Silver has identified additional occurrences of mineralization in the footwall below the San Marcial fault/breccia package. The volcanics in the footwall display flow banded features typical of a lava dome geological setting and are cut by several dykes. They also possess silver-gold vein stockwork mineralization in contrast to the breccia mineralization of the main zone. Silver rich breccia style mineralization, returning high-grades have been identified in areas outside of the current resource indicating targets for potential drill follow-up.

Please click here to view our Discoveries Conference 2023 poster.


San Marcial Area – Geological Setting & Stratigraphy Summary