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Formula:   Cu2CO3(OH)2   mineral photo

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Crystal:   Monoclinic  
Hardness:   3.5-4  
Spec. Gr.:   4.0  
Streak:   Pale green  
Cleavage:   Basal, barely observed  
Location:   Tsumeb, Namibia  

Malachite rarely forms as crystals, and when it does, crystals are usually small and twinned. It is a secondary ore of copper and is found in copper deposits worldwide. It alters from other copper minerals by the action of carbonated waters. Malachite is frequently seen as a green coating on the copper roofs of buildings, which have been partially altered by carbon dioxide and moisture in the atmosphere. Rarely, malachite pseudomorphs after azurite, with fine crystals occurring at Bisbee, Arizona; Chessy, France; with perhaps the finest and largest found at Tsumeb, Namibia (formerly, South-West Africa). During the Middle Ages, malachite was reputed to have medicinal properties and was used, among other things, to treat colic and was a powerful erutic.

Bibliography: Alain, Eid, Minerals of the World, pg. 52.

Bancroft, Peter, Gem and Crystal Treasures, 1984, pg. 335-343.

University of California, Santa Barbara—Department of Earth Science
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