This specimen is calcite (water-white) .This pure calcite is waterwhite and the mineral, which is a calcium carbonate (CaCo3)in the rhombohedra system. The crystals have prismatic habit and strong clevages a golden yellow and colourless.Sample:Calcite(waterwhite) Weight:493.9gramsHardness(H)=3 on Moh&＃39;s scale.Specific gravity(SG)=2.71.Refractive index (RI)=1.658 for the ordinary ray and 1.486 for the extraordinary ray.Double refraction (DR)= the ordinary ray is seen with difficulty much depending on the granula size of the calcite crystals.