These dioptase crystals are from the Tsumeb Mine, Tsumeb, Otjikoto Region of Namibia. This is an ore pipe deposit that is mined for copper lead and other metals. It is over 3000 feet deep and contains two oxidation zones. Over 300 mineral species have been identified at the mine including, world class, dioptase. It is a silicate containing the elements Cu, Si, O and H. This specimen consists of crystalline calcite matrix that hosts several bright dioptase crystals up to approximately 11 mm across. The dioptase are emerald green and translucent. The piece measures 1 1/2 x 1 1/4 x 3/4 inches or 38 x 32 x 19 mm.