Clinoclase Locality: Mammoth Mine (Mammoth shaft), Tintic District, East Tintic Mts, Juab County, Utah, USA (Locality at mindat.org) Size: 10.1 x 7.6 x 4.8 cm. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Clinoclase
Also known as: Clinoclasite.
A rare dark-green hydrous copper arsenate forming acicular crystals in the weathered zone above copper sulfide deposits.
Intro adapted from Wikipedia (CC BY-SA).
Clinoclase is an IMA-recognized mineral species in the arsenate class, with the chemical formula Cu₃(AsO₄)(OH)₃.
It crystallizes in the monoclinic crystal system (space group P2_1/c).
Key properties: Mohs hardness 2.5–3; specific gravity 4.38; typically blue or green; Bluish green streak; Vitreous, pearly on cleavages luster; optically biaxial.
IMA symbol Cno, grandfathered status — known before the IMA’s founding, named in 1830.
A rare secondary mineral found in the oxidized zone of some arsenic-rich hydrothermal base-metal deposits.
It is found associated with Olivenite, cornwallite, cornubite, conichalcite.
Its name comes from the Greek for to incline and to break, remarking the oblique basal cleavage.
Collections: Collector Favorites, Rare & Remarkable.