Plancheite

Locality: Kolwezi District, Katanga Copper Crescent, Katanga (Shaba), Democratic Republic of Congo (Zaïre) Dimensions: 5.9 cm x 3.2 cm x 2.6 cm”Courtesy of Rob Lavinsky, The Arkenstone, www.iRocks.com”

Chemical Formula: Cu8(Si8O22)(OH)4·H2O
Locality: Tantara and Kambowe, Zaire.
Name Origin: Named after J. Planche who brought it from Africa.

Plancheite is a hydrated copper silicate mineral with the formula Cu8(Si8O22)(OH)4·H2O. It is closely related to shattuckite in structure and appearance, and the two minerals are often confused.

Structure

Plancheite is a chain silicate (inosilicate), with double chains of silica tetrahedra parallel to the c crystal axis. It occurs as sprays of acicular or fibrous radial clusters, with fibers extended parallel to the chains, i.e. along the c crystal axis; it can also form tiny tabular or platy crystals. It is a member of the orthorhombic crystal class m m m (2/m 2/m 2/m), which is the most symmetrical class in the orthorhombic system.

History

Discovery date : 1908
Town of Origin : MINDOULI
Country of Origin : ZAIRE ex-CONGO

Optical properties

Optical and misc. Properties:  Translucide
Refractive Index: from 1,69 to 1,74
Axial angle 2V: 88,5°

Physical properties

Hardness : 6,00
Density : from 3,65 to 3,80
Color: pale blue; dark blue; green blue; greenish blue
Luster: adamantine; silky; unpolished; bright; satin-like
Streak : pale blue
Cleavage : NO

Photos :

Brochantite (XLS!) with Plancheite Musinoi Mine, Kolwezi, Democratic Republic of Congo Small Cabinet, 9 x 5.6 x 3.7 cm “Courtesy of Rob Lavinsky, The Arkenstone, www.iRocks.com”
Dioptase, plancheite 4.5×3.4×3.4 cm Tsumeb, Naibia Copyright © David K. Joyce Minerals
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