Aurichalcite, basic zinc copper carbonate, formula (Zn,Cu)₅(CO₃)₂(OH) ₆.

Crystal system: Orthorhombic (crystal form usually needles or finely foliated crystals).
Hardness: 2
Density: 3.9
Colour: Light blue or blue-green.
Streak: Lighter than the colour.

Aurichalcite is a secondary mineral formed in the oxydation zones of copper and zinc deposits. It is found in association with other zinc minerals hydrozincite, smithsonite and hemimorphite. Occurrence is rare. Particularly fine crystalline specimens are found at Lavrion in Greece. The name derives from the ancient Greek for 'mountain copper' (oros = mountain, chalcos = copper); the spelling of 'oros' no doubt having been corrupted to 'auri' over time.

The specimen shown in the picture came from the 79 Mine, Hayden, Gila County, Arizona, USA.