Chalk is a soft, fine-grained white limestone. It was formed as a mud on the bottom of an ancient sea. It differs from many pure, fine-grained limestones only in still being soft and easily rubbed off. That is, it did not change into hard rock.
Chalk consists largely of tiny shells and crystals of calcite. Both of these materials are made up of the compound calcium carbonate. The white cliffs of Dover are thick layers of chalk. This gave the name Albion to England. Albion probably means white land. Chalk deposits in western Kansas contain the preserved skeletons of extinct sea serpents, flying reptiles, birds, and fishes.
Most deposits formed during the Cretaceous Period of time. The Cretaceous Period got its name from the Latin word for chalk, creta.
Chalk is made into whiting, a substance used to manufacture rubber goods, paint, putty, soft polishing powders, and tooth powder. Industry also uses chalk, like any other limestone, in making portland cement and as a top dressing for soils. Chalk is also used to make crayons for writing on chalkboard.
