Atacamite
Image: <a href="//commons.wikimedia.org/wiki/User:Iifar" title="User:Iifar">Ivar Leidus</a> (CC BY-SA 4.0)
Mineral NameAtacamite
Chemical FormulaCu2Cl(OH)3
Mohs Hardness3
Crystal Systemorthorhombic
Lusteradamantine
Streak Colorgreen
Cleavageperfect on {010}
Fractureconchoidal to uneven
Specific Gravity3.76
Colorsemerald green, dark green, blackish-green
Transparencytransparent to translucent
Type LocalityMt Gunson mines, South Australia
Mineral GroupHalides
Usescollector's specimens, minor copper ore
Associated Mineralsmalachite, azurite, chrysocolla
Rarityuncommon
Description
This specimen features a dense covering of sparkling, deep emerald-green, acicular atacamite crystals forming a druse over a malachite matrix. The crystals are slender and radiating, giving the surface a velvety yet spiky appearance.
Geological Context
Atacamite is a secondary copper mineral typically found in the oxidized zones of copper deposits, particularly in arid coastal regions where chloride-rich waters are present. It forms from the alteration of primary copper sulfides.
