Exellent Crystals of Clinoclase
Clinoclase Crystals. Photo Copyright © Elmar Lackner

Clinoclase : Cu3(AsO4)(OH)3
Crystal System: Monoclinic
Hardness: 2.5 - 3.0
Tenacity: brittle

Locality: Tin stope, Majuba Hill Mine (Majuba Mine; Mylar Mine; Tin Mine; Nevada Bureau of Mines and Geology sample sites 2844 & 2846), Antelope District, Pershing Co., Nevada, USA

Clinoclase is a rare secondary copper mineral and forms acicular crystals in the fractured weathered zone above copper sulfide deposits. It occurs in vitreous, translucent dark blue to dark greenish blue colored crystals and botryoidal masses. The crystal system is monoclinic 2/m. It has a hardness of 2.5 - 3 and a relative density of 4.3. Associated minerals include malachite, olivenite, quartz, limonite, adamite, azurite, and brochantite among others.

Abichite is another name for clinoclase.