Copper

specimen number:
2292344

location:
Ray Mine, Pinal Co., Arizona, USA

description:
Attractive crystallized grouping of native copper with little attached matrix. Classic material for this locality. Minor cuprite appears to be present.

The Ray mine, situated in Pinal County, Arizona, is a major copper deposit located within a classic Laramide-age porphyry copper system. The geology of the deposit is centered around the Granite Mountain Porphyry, which intruded older Precambrian Pinal Schist and Apache Group diabase sills approximately 60 million years ago. Hydrothermal alteration associated with this magmatic event introduced primary copper sulfides, which were later subjected to weathering and supergene enrichment, forming a thick, high-grade chalcocite blanket over the primary mineral zones. Historically, mining claims in the district were first located in the 1870s, but large-scale operations did not succeed until the Ray Consolidated Copper Company initiated mechanized underground block-caving methods in 1911. By 1917, the site was one of the top copper producers in Arizona. In 1948, the operator, Kennecott Copper, began stripping overburden to transition the site to an open-pit mine. Open-pit extraction fully replaced underground mining by 1955, eventually expanding to consume the historical mining town of Ray and forcing its residents to relocate to nearby Kearny. Today, the massive open-pit operation is owned and operated by ASARCO.

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