Malachite after Azurite

specimen number:
8311398

location:
Sacramento Mine, Bisbee, Cochise Co., Arizona, USA

description:
A sharp grouping of prismatic crystals of what were once azurite, these now replaced by green malachite. In great condition. Complete all around.

The Sacramento Mine, located in the Warren District of Bisbee, Arizona, is a historic copper deposit situated within the southern Mule Mountains. Geologically, it is a carbonate-replacement deposit where mineral-rich hydrothermal fluids interacted with the Mississippian-aged Escabrosa Limestone to form massive sulfide and oxide bodies along the contact of the Sacramento Hill porphyry stock. The mine is world-renowned for its exceptional pseudomorphs of malachite after azurite, which occur when changing chemical conditions cause the more stable green copper carbonate to replace the original sharp, deep blue azurite crystals while perfectly preserving their primary monoclinic form. Historically, the Sacramento Hill area was first identified as a major low-grade copper resource in the early 1900s, with stripping of the overburden beginning in 1917 to prepare for open-pit operations. Large-scale production commenced in 1923 and continued as a primary focus of the Copper Queen Branch of the Phelps Dodge Corporation until the pit was largely exhausted in 1929, though underground and related activities in the immediate vicinity persisted for several decades thereafter. Today, the site remains an essential part of the Bisbee mining landscape, famous for the rich secondary copper minerals that characterize the oxidation zones of this legendary district.

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