Formula: Cu8(Si8O22)(OH)4 · H2O

Colour: Pale blue to deep blue, pale greenish blue.

Lustre: Silky

Hardness: 6

Specific Gravity: 3.65 – 3.80

Crystal System: Orthorhombic

Name: Named by A. Lacroix in 1908 in honor of François Gilbert Planche (1866-1924), was an industrialist and a politician. He built dams and power plants, and founded several rail companies. In Africa, he constructed the Brazzaville line in Mindouli. He was also director of the French Congo Mining Company which opened copper mines in the area. He supplied the first samples for study.

Type Locality: Sanda Hills occurrences, Mindouli, Mindouli District, Pool Department – Republic of the Congo

A rare secondary copper silicate. May be confused with Shattuckite.