This is the well preserved dioptase crystals. Dimensions: 1.3 x 0.8 x 0.5″ (3.2 x 2 x 1.2cm). Weight – 0.2oz (7 grams). Origin: Kazakhstan.
Some information about dioptase:
Dioptase is an intense emerald-green to bluish-green copper cyclosilicate mineral. Its formula is CuSiO3·H2O (also reported as CuSiO2(OH)2). It has a hardness of 5. Its specific gravity is 3.28–3.35, and it has two perfect and one very good cleavage directions. Additionally, dioptase is very fragile and specimens must be handled with great care. It is a trigonal mineral, forming 6-sided crystals that are terminated by rhombohedra.
Dioptase is an uncommon mineral found mostly in desert regions where it forms as a secondary mineral in the oxidized zone of copper sulfide mineral deposits. However, the process of its formation is not simple, the oxidation of copper sulfides should be insufficient to crystallize dioptase as silica is normally minutely soluble in water except at highly alkaline pH. The oxidation of sulfides will generate highly acidic fluids rich in sulfuric acid that should suppress silica solubility. However, in dry climates and with enough time, especially in areas of a mineral deposit where acids are buffered by carbonate, minute quantities of silica may react with dissolved copper forming dioptase and chrysocolla.