Miargyrite with Quartz

specimen number:
9302269

location:
Fresnillo, Zacatecas, Mexico

description:
Bright metallic micro crystals of miargyrite across the top of a crystallized quartz matrix. Choice example for the species from this famous Mexican locality.

The Fresnillo district, located in the central part of Zacatecas, Mexico, is home to one of the world's oldest and most productive silver mining operations. Geologically, it is a world-class epithermal vein system where mineral-rich fluids deposited silver, lead, and zinc within fault zones cutting through Cretaceous sedimentary and volcanic rocks. While the district is primarily famous for its massive production of native silver and acanthite, it is also a significant locality for rare silver sulfosalts like miargyrite. Miargyrite from Fresnillo typically occurs as metallic, iron-black to dark steel-gray crystals that may show a deep red internal reflection when viewed under intense light. These crystals often exhibit a complex monoclinic habit with a sub-metallic luster and are frequently associated with other silver minerals and quartz. Historically, mining at Fresnillo dates back to the 1550s, shortly after the Spanish conquest, and the district has remained in nearly continuous operation for over four centuries. Today, the Proano Mine at Fresnillo continues to be a global leader in silver production, and it remains a vital source for both industrial silver and high-quality specimens of complex silver-bearing species.

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