Clinoclase: Information & Facts
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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.
It forms in the oxidized zones of copper deposits where arsenic is present, often alongside minerals like malachite, azurite, and olivenite. The mineral crystallizes in the monoclinic system, typically appearing as slender, needle-like or prismatic crystals, though it can also occur in radiating clusters, crusts, or massive forms. Its color ranges from deep azure-blue to emerald-green or even bluish-black, with a vitreous to subadamantine luster that can appear almost gem-like in well-formed specimens.
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.
Wheal Gorland, St Day United Mines (Poldice Mines), Gwennap, Camborne - Redruth - St Day District, Cornwall, England, UK
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| Clinoclase crystals, from Majuba Hill Mine, Pershing County, Nevada. |
First discovered in Cornwall, England, in the early 19th century, clinoclase has since been found in other notable localities, including the world-famous Tsumeb Mine in Namibia and the historic mining district of Lavrion, Greece. In the U.S., specimens have been reported from Arizona and Nevada. Due to its scarcity and vibrant color, clinoclase is highly prized by mineral enthusiasts, though it lacks significant economic value. Its formation provides valuable insight into the geochemical processes occurring in oxidized copper-arsenic deposits.
While not an economically significant copper ore, clinoclase is highly prized by mineral collectors for its vivid colors and rarity. Its formation provides valuable insights into the geochemical processes in oxidized copper-arsenic deposits.
