Quartz (SIL-0023)

specimen number:
9273108

location:
Guanajuato, Mexico

description:

Very attractive lustrous deep purple sparkling crystals of quartz, the variety known as amethyst, measuring to 0.5 cm in size covering the top of matrix. In good condition with very minimal micro-damage present. The color is outstanding for the locality and species.

The Guanajuato mining district, located in central Mexico, represents one of the world's most prolific historic producers of silver and gold. Geologically, the district is situated within the southern part of the Sierra Madre Occidental volcanic province and developed inside a mid-Tertiary volcano-sedimentary sequence. The precious metal mineralization occurs within intermediate-to-low sulfidation epithermal veins and stockworks, which are clustered into three major fault-controlled systems known as the La Luz system, the Sierra (or El Cubo) system, and the central Veta Madre ("Mother Lode") vein. These massive deposits formed during the Oligocene epoch, roughly between 30.7 and 27.0 million years ago, following a period of intense ignimbrite volcanism and subsequent caldera resurgence. Mining history in the region began during the Spanish colonial expansion between 1540 and 1550, with the definitive discovery of major silver-gold deposits occurring around 1552 and escalating by 1557. Throughout the 16th, 17th, and 18th centuries, operations heavily utilized the mercury amalgamation process to process the ore, turning the region into a cornerstone of New Spain's economy. Following centuries of colonial production and a brief decline during the Mexican War of Independence, extraction was revitalized in the late 19th and 20th centuries by foreign capital and later by local mining cooperatives. Large-scale commercial extraction and active deep-shaft mining have persisted continuously into the 21st century, yielding a cumulative historical output estimated at 37,000 metric tonnes of silver and 135 metric tonnes of gold.

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