Quartz with Pyrite

specimen number:
2292168

location:
Guanajuato, Mexico

description:
Attractive glassy partly gemmy purple crystals of quartz to 1.5 cm in size across the top of matrix. Micro crystals of sparkling golden pyrite are scattered throughout. This is the variety of the species often called amethyst.

The Guanajuato mining district, located in the central highlands of Guanajuato, Mexico, is an extraordinarily rich silver and gold district that has been heavily quarried and mined since the mid-sixteenth century. Geologically, the deposit is composed of Oligocene-aged epithermal vein systems, most notably the massive Veta Madre (Mother Lode), which cut through a complex sequence of Mesozoic metamorphic rocks and Tertiary volcanic conglomerates. These veins precipitated high-grade silver sulfides, native gold, and electrum within quartz and carbonate gangue during periods of intense regional volcanic activity. Spanish colonists initiated formal underground mining at the site in 1548 following the discovery of the San Bernabe vein, leading to the development of historic operations like the Valenciana mine, which alone produced a significant percentage of the world silver supply in the eighteenth century. Underground operations expanded through centuries of continuous exploitation, adapting from traditional hand-quarrying methods to massive mechanized modern extraction, with various mines across the district remaining active under international mining firms into the 2020s.

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