Project Summary

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The Plomosas Property is located within 5 kilometres of GR Silver’s San Marcial Property in the Rosario Mining District, Sinaloa, providing opportunities for future development of both projects. The Plomosas Property lies in a geological setting similar to that of the San Dimas Mining District which has produced over 11Moz gold and 600Moz silver and is also located along the western edge of the Sierra Madre Occidental. The Plomosas Property includes a past-producing silver–gold–lead–zinc (“Ag-Au-Pb-Zn”) underground mine (“Plomosas Mine”), operated by Grupo Mexico S.A de C.V., inside 8,515 hectares of mining concessions with numerous drilled areas. The combination of infrastructure and historical data presents upside potential for resource definition and future exploration. The Plomosas Property, together with the San Marcial Property, provides GR Silver control of 9,764 hectares, covering most of the Ag-Au-Pb-Zn mineralized zones in the eastern section of the Rosario Mining District. The following royalty interests and purchase rights are related to the Plomosas Property: 2% NSR to Corporación First Majestic (a subsidiary of First Majestic Silver Corp.) with a buyback 1% NSR for US$1,000,000 and 1.75% – 3.5% net production and sales royalty to Industrial Minera México (a subsidiary of Grupo Mexico) based on the price of zinc.

In August 2021, GR Silver announced an initial NI 43-101 mineral resource estimate for the Plomosas Property. The estimate combined resources from the Plomosas Mine Area and the San Juan Area and is shown in the resource table below. Full details are contained in the Technical Report.

Numbers may be rounded. * Silver Equivalent (“AgEq”) calculations using US$20.00/oz Ag, US$1,600/oz Au, US$0.90/lb Pb, US$1.10/lb Zn and US$3.00/lb Cu, with metallurgical recoveries of Ag – 74%, Au – 86%, Pb – 69%, Zn – 75% and Cu – 80%. 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)


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Plomosas is located 98 kilometres southeast of Mazatlán (straight line) and 198.5 kilometres by road. The property lies within an erosional window into the regional geology, exposing andesite and andesitic tuffs, rhyodacites and dacites, with associated volcanic breccias and lapilli tuffs of the Lower Volcanic Series, below a thick sequence of silicic ignimbrites.

The mineralization exhibits the alteration, textures, mineralogy and geometry characteristics of a low sulphidation epithermal silver-gold and base metal (lead-zinc) vein/breccia deposit, with banded quartz-carbonate veining accompanied by potassic adularia-sericite and moderate argillic alteration. Multiple phases of mineralization are evident, as shown by the overprinting of sulphide-rich mineralization over previous gold and silver-gold mineralized zones.

Most of the historically mined zones consist of quartz-galena-sphalerite +/- pyrite-chalcopyrite, magnetite veins and gold-silver rich stockworks. There is evidence of three stages of quartz sulphide mineralized with brecciation associated with the second stage. The various high-grade silver-gold stockwork systems appear to be low sulphidation epithermal mineralization, related to low angle dilation zones and fault intersections. There is a predominance of gold-rich stockworks in the silver-gold-base metal vein breccia foot wall and silver-rich in its hanging wall.



San Juan Overview - Aug 28, 2021

Plomosas Overview - Sep 14, 2020

San Juan Area Plomosas Historic Drilling High Grade Breccia Drill Hole SJS 18 11 - Jan 12, 2021

San Juan Area Plomosas Historic Drilling High Grade Hydrothermal Breccia Drill Hole SJS 18 01 A (Jan 12, 2021)

Plomosas Mine Area High Grade, Surface Mineralization Drill Hole PLS 20 03 (Jan 12, 2021)

Plomosas Mine Area Underground Mineralization Discovery Drill Hole PLI 20 04 (Jan 12, 2021)

Yecora Vein Discovery, Plomosas Project (Nov 24, 2020)

San Juan Surface Drilling (Nov 1, 2020)




Plomosas Mine Level 775: Conceptual 3D Model (Sept 28, 2020)

3D Map of GR Silver's Plomosas Project (Aug 19, 2020)