Malachite

specimen number:
2102366

location:
Dallas Shaft, Bisbee, Cochise Co., Arizona, USA

description:
Silky green crystallized malachite throughout matrix. In good condition.

The Dallas shaft, situated within the Warren Mining District in Bisbee, Cochise County, Arizona, was a major underground copper extraction site that served as a critical production hub for the legendary Copper Queen Consolidated Mining Company. Geologically, the shaft penetrated a deeply buried, structurally complex environment where Paleozoic carbonate rocks, particularly the Escabrosa and Martin limestones, were intruded by the Jurassic-age Sacremento Hill porphyry stock. High-grade copper mineralization occurred as massive sulfide replacement bodies containing chalcopyrite and bornite, along with spectacular secondary oxidation zones rich in malachite, azurite, and native copper, which were localized along faults, fractures, and contact breccias. Historically, sinking of the Dallas shaft began in 1902 to tap into deep-seated ore bodies lying southeast of Sacramento Hill, and it quickly became an integral part of the sprawling Copper Queen operations managed by Phelps Dodge Corporation. The shaft was pushed to a total depth of 2000 feet, featuring extensive underground connections to adjacent mines to facilitate ventilation, drainage, and efficient ore haulage during decades of heavy industrial production. The Dallas shaft remained in continuous operation through the peak years of the district before changing economics and the transition toward large-scale open-pit mining at the nearby Lavender Pit led to the gradual winding down of deep underground extraction, culminating in the permanent closure of the shaft in the mid-1970s when Phelps Dodge ceased all underground operations in Bisbee.

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