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
Cleavageperfect on {010}
Fractureconchoidal
Specific Gravity3.76
Colorsemerald-green, dark green, blackish-green
Transparencytranslucent
Type LocalityLa Farola Mine, Cerro Pintado, Las Pintadas district, Tierra Amarilla, Copiapó Province, Chile
Mineral GroupHalides
Usesminor copper ore, collector
Associated Mineralscuprite, malachite, chrysocolla, brochantite, gypsum
Rarityuncommon
Description
This specimen showcases radiating aggregates of dark emerald-green to blackish-green acicular atacamite crystals, some exhibiting a strong adamantine luster, on a lighter green matrix.
Geological Context
Atacamite is a secondary mineral formed in the oxidized zone of copper deposits, particularly in arid climates where chloride-rich solutions are present, often as an alteration product of primary copper sulfides.
