Copper (CU-0036)

specimen number:
9273056

location:
Chino Mine, Santa Rita, Grant Co., New Mexico, USA

description:

A superb example for the species from this New Mexico locality, a large sharp twinned crystal grouping of native copper without matrix. In super condition all around.

The Chino mine, also known as the Santa Rita mine, is located in Grant County, New Mexico, and stands as one of the oldest and largest open-pit copper quarries in North America. Geologically, it is a classic porphyry copper deposit formed during the Late Cretaceous and Early Paleocene epochs, centered around a highly altered quartz monzonite porphyry stock that intruded into Paleozoic and Mesozoic sedimentary rocks, creating a rich zone of disseminated copper sulfides alongside significant skarn mineralization in the surrounding limestones. The deposit features a famous secondary enrichment zone where descending groundwater concentrated low-grade primary ores into rich chalcocite blanketing, complemented by a notable upper oxidation zone that yielded spectacular specimens of native copper, cuprite, and turquoise. Native Americans and early Spanish explorers mined the surface outcrops for centuries, with formal underground mining starting under Spanish colonial direction around 1801 to supply copper for coinage. The property transitioned into a massive, industrialized open-pit operation in 1910 under the direction of John M. Sully and the Chino Copper Company, pioneering steam-shovel extraction techniques that replaced the older underground shafts. Except for a few temporary suspensions driven by global economic downturns, such as during the Great Depression and brief market drops in the early twenty-first century, open-pit quarrying and heap-leach solvent extraction processing have run continuously under a sequence of corporate owners, including Kennecott, Phelps Dodge, and Freeport-McMoRan, which continues active, large-scale mining at the site today.

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