Gypsum
Gypsum belongs to the sulfate group. It contains calcium and sulfur. Its chemical formula is CaSO4 ·2 H2O .
Its crystals occur in several forms: tabular, lamellar, prismatic, and when translucent, they are called Selenite. Impurities give it beautiful colors of brown, reddish-brown, yellow, gray, or orange.
Gypsum has a low hardness, equal to 2/10 on the Mohs scale (10 for diamond), just slightly harder than talc. Its density is 2.3 (1 for water). The streak on the porcelain is white.
The massive variety is called Alabaster and allows for the fine carving of sculptures, which nevertheless remain very fragile. Selenite is a translucent variety of Gypsum, and Sericolite Gypsum is a fibrous variety of Gypsum with a silky appearance.
Gypsum is widely used in the production of plaster. The name Gypsum comes from the Latin word gypsum which means plaster .
