Calcite

Composition: CaCO3 Hardness: 3 Luster: Nonmetallic Streak: Colorless to White Cleavage Distinguishing Chararacteristics: Bubbles with hydrochloric acid, displays double refraction.

Calcite is a common mineral that makes up 4% of the earth's surface by weight. Calcite is commonly formed when calcium carbonate percipitates in water.