Malachite replacing Azurite

specimen number:
8282050

location:
Milpillas mine, Santa Cruz, Sonora, Mexico

description:

Extremely large grouping of double terminated azurite crystals measuring 8.0 cm in size, these now completely replaced by chatoyant green crystallized malachite, set beautifully up on a brecciated matrix. This is in super condition.

The Milpillas Mine is a copper mine located in the municipality of Santa Cruz in Sonora, Mexico, near the United States border. The deposit is a porphyry copper system with a large oxidized zone that produced important secondary copper minerals. Commercial mining began in 2006 and the mine became widely known among mineral collectors for exceptional specimens of azurite, malachite, cuprite, brochantite, and other copper minerals. During its relatively short period of operation the mine produced some of the finest azurite crystals ever found, making Milpillas one of the most famous modern mineral localities.

A pseudomorph is a mineral specimen in which one mineral replaces another while preserving the original crystal shape. Malachite after azurite forms when azurite is chemically altered through exposure to water and carbon dioxide, causing the azurite to convert to malachite while retaining the original azurite crystal form. This process commonly occurs in the oxidized zones of copper deposits. The resulting specimens show the sharp crystal shape typical of azurite, but the material is composed entirely of green malachite.

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