jip'sum, the name generally given calcic sulphate. It is found in a compact state as alabaster (See ALABASTER), or crystallized as selenite, or in the form of a soft, chalky stone, which in a very moderate heat changes to a very fine white powder, extensively used under the name of plaster of Paris. This last is the most common and is found in great masses near Paris; large beds are also found in Nova Scotia, Virginia, Michigan, New York, Iowa and Ohio. It may be geologically of any age, but it occurs abundantly in the more recent sedimentary formations and is even now forming, as a deposit from water holding it in solution; from the decomposition of iron pyrites, when the sulphuric acid combines with lime, or from the action of sulphurous vapors in volcanic regions on rocks containing lime. When gypsum occurs without water it is called anhydrite, but in its most ordinary state it is combined with water. Gypsum, pulverized by grinding or burning, has been used with good effect as a fertilizer, especially as a top dressing for meadows. See FERTILIZERS.