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.