Calcite

specimen number:
8311566

location:
Palmarejo Mine, Chihuahua, Mexico

description:

A large lustrous translucent twinned crystal of calcite 13.0 cm in height coming off matrix with many much smaller crystals of calcite. This is in great condition, the only cleaving present is along the extreme edges of the matrix to some of the smaller crystals. The large twinned crystal is perfect all around. Fine museum size piece that displays well.

The Palmarejo mine, located in the Chinipas Municipality within the southwestern corner of Chihuahua, Mexico, is a major, highly productive silver and gold mining operation situated in the prolific Sierra Madre Occidental metal belt. Geologically, this high-grade deposit consists of low-sulfidation epithermal vein systems, breccias, and structural fractures hosted within a thick sequence of late Oligocene to early Miocene volcaniclastic rocks and flows, mostly dominated by shallow-dipping andesite that is cut by younger rhyolite domes and dikes. Mineralization is driven by ancient hydrothermal activity that precipitated precious-metal-bearing electrum and acanthite, along with base metal sulfides like sphalerite, galena, and chalcopyrite, within quartz-chalcedony veins, while also producing exceptional multi-generational calcite specimens sought after by mineral collectors. Historically, gold-bearing minerals were first discovered at the site in 1818, leading to a long era of intermittent, small-scale colonial and industrial underground extraction that included the construction of a metalworks facility and a narrow-gauge railway in 1892, before operations were completely suspended in 1912 due to the disruptions of the Mexican Revolution. Modern systematic exploration revived the district in 2003, and Coeur Mining purchased the property in 2007, commencing official commercial open-pit and underground mining in 2008 and starting up its large-scale processing mill in 2009. While open-pit extraction ceased completely in 2016, modern operations transitioned fully underground into a highly efficient complex utilizing mechanized stoping methods across several highly interconnected deposits, including the Guadalupe, Independencia, and La Nacion underground mines. Through 2026, the Palmarejo complex remains fully active, serving as Coeur Mining's flagship Mexican operation and an important global geological benchmark for studying active Cenozoic epithermal silver-gold enrichment systems within volcanic arc environments.

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