Quartz with Calcite

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A plate of crystallized quartz, scattered throughout are small crystals of calcite. In good condition.The Guanajuato mining district, located in central Mexico, is positioned at the transition zone between the Sierra Madre Occidental and the Trans-Mexican Volcanic Belt. The regional geology is characterized by a Mesozoic sedimentary basement overlain by Eocene conglomerates and Oligocene volcanic sequences. Extensional faulting approximately 30 million years ago created major fault systems, most notably the 25-kilometer-long Veta Madre, which served as conduits for hydrothermal fluids. These fluids deposited precious metals in low-sulphidation epithermal vein systems, producing immense concentrations of silver and gold. Spanish colonists began exploiting these deposits in the 1540s, and by the late 18th century, Guanajuato had become the world's leading silver-producing district, with the single Valenciana mine generating roughly 30 percent of the global silver supply. Mining remains an active and vital part of the local economy to this day.