Calcium sulfate dihydrate, found in a variety of forms as natural deposits (such as alabaster), which when heated and deprived of its moisture forms the substance known as plaster of Paris. Gypsum rates an index of 2 on Mohs Scale of Hardness. (pr. JIP-səm)Examples of objects carved from blocks of gypsum: Levant, Jericho, Small Vessel with Banded Neck Decoration (from Tomb J42), c. 1800-1550 BCE, gypsum, 3 1/8 x 2 3/8 inches (7.8 x 6 cm), Michael C. Carlos Museum, Emery U, Atlanta, GA. See vessel.