Natural Dioptase Specimens on Dolomite Matrix x 12 From Tantara Mine, Congo Tourmalinated A large 78 x 126 A large 78 x 126 x 165 mm sized natural Dioptase with Feldspar is a fairly rare and extremely beautiful Bright Emerald Green Copper Mineral formed from the action of the Cu content in the mineralised water in hydrothermal activities in the dolomite faults from the mantle It is a secondary copper silicate found in the oxidized zones of copper deposits These are nice compact sizes with perfectly polished top faces that reveal stunning crystalline drusy centres with the matrix left natural on the back and sides Chrysocolla and Azurite Dioptase On Dolomite from the Congo: Emerald Beauty Unveiled