Specimen of the Month
October 2014
Plancheite

Chemically, Plancheite is basic copper silicate.

Formula: Cu 8 (Si 4 O 11 ) 2 (OH) 2 .H 2 O

Crystal System: Orthorhombic

Hardness: 5.5

Density: 3.7

Colour: Blue or blue/green

Streak: Light blue

Plancheite is a rare translucent copper silicate occurring as a secondary mineral in oxidation zones. It forms as radial groups of needle-like, or fibrous, crystals. The mineral is named after J. Planche who discovered it in 1908 at Mindouli, in the former Republic of Congo and brought samples of the mineral back from Africa.

The specimen illustrated comes from M'sesa, Kata Unga, Zaire
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