Polybasite with Acanthite

specimen number:
9273030

location:
La Cata Mine, Guanajuato, Mexico

description:

A cluster of large thick polybasite crystals measuring to 2.0 cm in size, these hosting small crystals of acanthite throughout. This is in great condition.

The La Cata mine, situated within the historic northern suburbs of the city of Guanajuato, Mexico, is a legendary underground silver and gold mine celebrated for producing significant wealth and world-class mineral specimens. Geologically, this deposit is localized along the prolific Veta Madre (Mother Lode) fault system, a major regional epithermal vein structure that dips shallowly to the southwest and cuts through the Mesozoic-age Guanajuato Conglomerate and underlying volcanic tuffs. Mineralization occurred during Oligocene magmatic and tectonic activity, where boiling, low-to-intermediate sulfidation hydrothermal fluids ascended through the fault zone, depositing thick bonanza ore shoots rich in silver sulfides, electrum, and base metal sulfides enclosed within a gangue of quartz, adularia, and calcite. Historically, the La Cata workings were initiated by Spanish colonists during the mid-sixteenth century, shortly after the initial 1548 discovery of the district, and the mine achieved immense profitability in the late eighteenth century alongside the neighboring Valenciana mine. Operations survived multiple disruptions, including the Mexican War of Independence, and transitioned through British management, twentieth-century local miner cooperatives, and eventual corporate acquisition. Through 2026, the mine remains a productive unit under modern corporate consolidation, serving as an important geological anchor for studying structural controls and fluid dynamics in high-grade epithermal silver systems.

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