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substance (hydrated calcium sulphate) used in making plaster, late 14c., from Latin gypsum, from Greek gypsos "chalk," according to Klein, perhaps of Semitic origin (cf. Arabic jibs, Hebrew gephes "plaster").
A colorless, white, or pinkish mineral. Gypsum occurs as individual blade-shaped crystals or as massive beds in sedimentary rocks, especially those formed through the evaporation of saline-rich water. It is used in manufacturing plasterboard, cement, and fertilizers. Chemical formula: CaSO4·2H2O.