Dioptase

specimen number:
2102362

location:
Morenci Mine, Greenlee Co., Arizona, USA

description:
Green crystals of dioptase to 0.3 cm in size throughout all sides of matrix. In good condition with minimal micro-damage present.

The Morenci mine, located in Greenlee County, Arizona, is the largest producing copper operation in North America and ranks among the largest open-pit quarries in the world. Geologically, the site is a world-class Laramide-age porphyry copper deposit formed during the Paleocene to early Eocene epochs, when multiple waves of monzonitic porphyry stocks intruded into ancient Precambrian granite and Paleozoic to Mesozoic sedimentary rocks. This intense magmatic and hydrothermal activity generated extensive stockwork veinlets of primary sulfides like chalcopyrite and molybdenite, which were later altered by weathering to form a massive secondary supergene enrichment blanket dominated by chalcocite, as well as an upper oxidation zone rich in malachite, azurite, and chrysocolla. The historical timeline began in 1872 with the development of the first commercial claims, expanding into organized underground shaft mining by 1881 under companies like the Detroit Copper Company and the Arizona Copper Company, which were later consolidated under the Phelps Dodge Corporation. Facing declining ore grades, operators pioneered a massive transition to open-pit quarrying starting in 1937, with active bulk extraction officially launching in 1942. Phelps Dodge introduced large-scale solution extraction and electrowinning technology to the site in 1987, and following a corporate acquisition in 2007, current operator Freeport-McMoRan continues active, high-volume open-pit mining at the sprawling complex today.

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