Gypsum.—Technically, gypsum is a "native hydrated sulphite of calcium." In mineralogy it is classed as a "monoclinic mineral, ranging from transparent to opaque." It is usually colorless or white, though it is sometimes found gray, flesh-colored, yellow or blue. When found in transparent crystals it is called selenite; in the fibrous form it is known as satin spar; in fine-grained, translucent masses it is called alabaster; and in large beds of massive rock, mixed with clay, calcium carbonate, or other impurities, it constitutes the rock gypsum of commerce, which is sold as land plaster, or when calcined as plaster-of-paris. Its origin is due to the evaporation of sea water in enclosed lakes or bays cut off from the ocean, to deposits of thermal springs, or to volcanic action. Gypsum is abundant in Kansas, both in the form of rock gypsum and as a fine powder of sand or dirt in the beds of the streams and marshes, and is believed to have been deposited by the first method when Kansas was an inland sea. Volume XI of the reports of the geological survey of Kansas made by the University of Kansas, gives an exhaustive account of the origin, nature and distribution of gypsum within the state. (See Geology.)

Gypsum was first discovered in Kansas by Thomas C. Palmer, who settled in Marshall county in 1857. Noticing that some rocks he had used about his camp fire had burned to lime, he used the product to "chink" his cabin. Subsequent investigation disclosed the fact that the rocks were gypsum. The following year Gen. F. J. Marshall burned some of the same kind of lime and plastered a house at Marysville. In 1872 Judge Coon and his brother began the manufacture of plaster-of-paris with a five barrel kettle at Blue Rapids, and three years later a stone mill was erected, which was conducted for about twelve years. In 1887 two companies were organized at Blue Rapids for the manufacture of cement plaster, and one was organized at Hope, Dickinson county. A mill established at Salina in 1889 furnished the plaster for the buildings of the Columbian exposition at Chicago in 1893. This brought Kansas gypsum to the notice of builders, and in 1898 the American Cement Plaster company was organized at Lawrence. Factories have since been established at Burns, Marion county; Kansas City, Mo.; and Wymore, Neb., all of which use large quantities of gypsum from the Kansas deposits. The United States Gypsum company, with offices in Boston, Cleveland, Chicago, Minneapolis, Minn., and San Francisco, manufacture a gypsum hollow tile for fireproofing, which has found favor with the architects of the country, and it is certain that the next few years will witness a great development of the Kansas gypsum fields.