Formula: Cu2Cl(OH)3
Specific gravity: 3.77
Hardness: 3 to 3½
Streak: Apple green
Colour: Bright green, dark emerald-green to blackish green; shades of green in transmitted light.
Solubility: Easily soluble in acids
Common impurities: Ca,Co

Hydrothermal environments

Atacamite is a secondary copper mineral formed through the oxidation of other copper minerals, especially in arid, saline conditions. It is also found in fumarolic deposits and as a weathering product of sulphides in subsea black smoker deposits (HOM).
Associated minerals include cuprite, brochantite, linarite, caledonite, malachite, chrysocolla, paratacamite and botallackite (HOM).
Atacamite may alter to malachite and chrysocolla, creating pseudomorphs (Mindat).

At Broken Hill, New South Wales, Australia, atacamite is associated with cerussite, chalcocite and chrysocolla (AJM 03.1.34).

At Northparkes, New South Wales, Australia, atacamite occurs in quartz monzonite associated with malachite and azurite (AJM 10.2.55 0.

At the Cams mine (now abandoned), Lake Miranda, Western Australia, atacamite was found on the dumps on limonite-coated quartz (AJM 20.1.51-54).

At the Surprise lead mine, Northampton lead-copper field, Western Australia, atacamite forms thin surface coatings on galena (AJM 18.1.39).

At the Lily mine, ICA department, Peru, atacamite occurs included in gypsum (Minrec 42.2.168).

At Bisbee, Arizona, USA, atacamite commonly occurs associated with cuprite nodules. It has been found in a cuprite nodule associated with spangolite, and separately associated with spangolite and claringbullite (Minrec 43.1 supplement, pps 14, 17, 33).

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