Atacamite
Image: <bdi><a href="https://www.wikidata.org/wiki/Q56247090" class="extiw" title="d:Q56247090"><span title="mineral collector and dealer">Robert M. Lavinsky</span></a></bdi> (CC BY-SA 3.0)
Mineral NameAtacamite
Chemical FormulaCu2Cl(OH)3
Mohs Hardness3
Crystal Systemorthorhombic
Lusteradamantine
Streak Colorapple-green
Cleavagegood on {010}
Fractureconchoidal
Specific Gravity3.76
Colorsdark green, emerald-green, blackish green
Transparencytransparent
Type LocalityLily Mine (Lilly Mine), Pisco Umay, Ica Department, Peru
Mineral GroupHalides
Usesminor copper ore, collector
Associated Mineralsgypsum, malachite, azurite, chrysocolla, cuprite
Rarityuncommon
Description
This specimen features sharp, dark emerald-green atacamite crystals, some acicular, growing on and within translucent to transparent gypsum crystals, creating a striking contrast.
Geological Context
Atacamite is a secondary mineral typically found in the oxidized zone of copper deposits, particularly in arid climates. It forms through the alteration of primary copper sulfides in the presence of chloride-rich solutions.
