This sample of plancheite is displayed in the Smithsonian Museum of Natural History. Plancheite is a silicate mineral of copper with the composition Cu8(Si4O11)2(OH)4.H2O. The sample at left is about 20 cm across and is from D. R. Congo. It is described as plancheite with dioptase.
Mindat describes plancheite as a rare secondary copper silicate. The bluegreen is its typical color.