Plancheite, basic copper silicate,
Formula Cu₈Si₈O₂₂(OH)₂.H ₂O

Crystal system: Orthorhombic
Hardness: 5.5
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.