Plancheite, basic copper silicate,
Formula Cu8Si8O22(OH)2.H 2O
Density: 3.7 gms/cm3
Colour: Blue or blue-green
Streak: Light blue
Plancheite is a rare, translucent copper silicate occurring as a secondary mineral in oxydation zones. It forms as radial groups of needle-like or fibrous crystals. Plancheite is named after J. Planche who brought samples of the mineral back from Africa.
This specimen of Plancheite comes from M'sesa, Katanga, Zaire.