Clinoclase: Information & Facts

Clinoclase: Information & Facts. Photo Copyright © Tóth László/Stone Ásványfotós

Clinoclase is a rare secondary copper mineral. It was first known from the Wheal Gorland Mine (now closed), a producer of many fine, rare and world-reknowned secondary minerals. Clinoclase has a beautiful dark blue to dark greenish blue color. Although usually small, its crusts of acicular crystals make for very attractive specimens as they coat all the nooks and crevices of a fractured host rock. A specimen of clinoclase is a pleasure to own by any serious collector of rare minerals.

Properties of Clinoclase

Chemical Formula:  Cu₃AsO₄(OH)₃

Class: Phosphates
Color is dark blue and with shades of green.
Luster is vitreous.
Transparency: specimens are translucent.
Crystal System: is monoclinic; 2/m
Crystal Habits include acicular crystals in radiating and near botryoidal crusts. Individual crystals of any size are rare, but when found are tabular or prismatic with small triangular faces modifying the crystals.
Cleavage is good in one direction.
Fracture is lamellar.
Hardness is 2.5 - 3
Specific Gravity is approximately 4.3 (heavy for translucent minerals)
Streak is bluish green.
Associated Minerals are malachite, olivenite, quartz, limonite, adamite, azurite, brochantite and other rare secondary copper ore minerals.
Other Characteristics: slightly soluable in hydrochloric acid.
Notable Occurrences: Cornwall, England; Libethen, Romania; Zaire; Russia; California, Utah and Arizona, USA.
Best Field Indicators: color, streak, crystal habits, associations and density.

Type Locality
Wheal Gorland, St Day United Mines (Poldice Mines), Gwennap, Camborne - Redruth - St Day District, Cornwall, England, UK