Clinoclase

Formula: Cu3(AsO4)(OH)3

Colour: Blue, greenish-blue, dark green-black; blue-green in transmitted light

Lustre: Vitreous, Pearly

Hardness: 2½ – 3

Specific Gravity: 4.38

Crystal System: Monoclinic. Its crystals can be elongated or tabular, and occur as single, isolated crystals, or it can be found in aggregates forming rosettes, or as crust or coatings with a fibrous structure,

Name: Named in 1830 by August Breithaupt from the Greek κλίυειυ = “to incline” and κλαυ = “to break,” in allusion to its oblique basal cleavage.

Type Locality: Wheal Gorland, St Day, Cornwall, England, UK

Clinoclase is a secondary mineral in the oxidized zones of deposits containing copper sulfides.