Dioptase Crystals On Calcite Minerals 9:46 PM A+ A- Print Email Dioptase | #Geology Formula: CuSiO3 · H2O System: Trigonal Colour: Emerald Green, blue-green Lustre: Vitreous Hardness: 5Locality: Tantara Mine, Kakounde, Likasi, Shaba Congo D.R. by usageology on Flickr.