These samples of dioptase are on display at the Smithsonian Museum of Natural History. Dioptase is a silicate mineral of copper with the composition CuSiO3.H3O. The sample at left is about 16x14 cm and is from Reneville, Congo.
This sample is described as dioptase with calcite. It is about 10x14 cm and is from Guchab, Namibia.
This dioptase sample is about 18x22 cm and is from Brazzaville, Congo.