CHALK. In geology chalk is a soft, friable, finely granular variety of limestone or car bonate of lime, and may in color range from pure white to grayish or buff. It is a marine deposit, composed principally of the shells of foraminifera. In the United States are some great beds of chalk of Upper Cretaceous Age. One is exposed for 250 miles from Austin to Sherman, Tex., and is nowhere much fess than 600 feet thick. Chalk beds of the same age, Colorado stage, are found in Arkansas, Kansas and in Montana, while the great chalk belt of Texas extends southwest from Austin into Mexico, being found in the states of Chihuahua, Coahuila and Tamaulipas. In Arkansas and Texas this chalk formation and its associated chalky marls is being developed as furnishing excellent material for making Portlant cement. No statistics of the amount thus used at present are available. In England the Upper Cretaceous series is marked by great beds of chalk and chalky limestones, and includes the Cenomanian, Turomain and Senonian stages. Such strata
extend across England from Fla.mborough Head on the east coast to west of Dover on the south coast. The chalk-mining industry of England is of importance, the total amount of chalk pro duced being about 4,500,000 tons annually. Part was used for cement-making and part for mak ing refined chalk. When freed from grit by washing, it is called whiting, and is used for cleaning silver and making putty. When mixed with some binding substance it is used as a marking material. It is also used in farming to improve the texture of the soil. When puri fied it is also used to allay acidity of the stomach. (See CEMENT; CRETACEOUS SYSTEM; Lam.) Consult (United States Geological Sur vey Report, 1900-01,) Part III; The Chalk of Northwestern Arkansas.)