GIPS

Gips, or gypsum, is a common soft sulfate mineral with the chemical formula CaSO4·2H2O, calcium sulfate dihydrate. The name derives from the Greek gypsos, meaning chalk. When gypsum is heated to remove part of its water, it forms plaster of Paris, CaSO4·0.5H2O, used as a settable material in construction and sculpture.

Gips occurs in sedimentary rocks formed by the evaporation of saline waters. It is mined worldwide and used directly as a raw material or processed into plaster products. In nature, it appears in several varieties, including selenite (transparent crystals), alabaster (fine-grained, translucent stone), and satin spar (fibrous).

Physical properties of gips include a Mohs hardness of about 2, perfect cleavage in one direction, and a white, gray, or colorless appearance that may be stained by impurities. It is relatively soluble in water, and finely ground gips reacts with water to form plaster. The material is lightweight and can be readily worked for casting and molding.

Uses of gips are widespread. It serves as a primary component of plaster and plasterboard (drywall), a set-retarder in cement manufacture, and a material for dental casts and sculpture. In industry, gypsum is also produced as FGD gypsum from flue-gas desulfurization, an important byproduct of pollution-control processes that is used in construction and agriculture.

Health and safety considerations are minimal with intact rock, but breathing gypsum dust can irritate the respiratory tract. Environmental aspects include responsible management of mining and the use of recycled or byproduct gypsum in construction.