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chalk, soft, fine-grained, easily pulverized, white-to-grayish variety of limestone. Chalk is composed of the shells of such minute marine organisms as foraminifera, coccoliths, and rhabdoliths. The purest varieties contain up to 99 percent calcium carbonate in the form of the mineral calcite.
Chalk is a biological limestone derived from the tiny calcium carbonate shells of foraminifera and the calcareous remains of marine algae. It is soft, friable, porous, permeable and usually white to light gray in color.
Jun 8, 2018 · chalk Mineral, mainly calcium carbonate (CaCO 3), formed from the shells of minute marine organisms. It varies in properties and appearance; pure forms, such as calcite, contain up to 99% calcium carbonate .
A soft, white, gray, or yellow limestone consisting mainly of calcium carbonate and formed primarily from the accumulation of fossil microorganisms such as foraminifera and calcareous algae. Chalk is used in making lime, cement, and fertilizers, and as a whitening pigment in ceramics, paints, and cosmetics.
In its natural state chalk is a relatively soft, white, fine-grained variety of limestone. It is composed primarily of the shells—calcium carbonate (CaCO 3 )—of microscopic one-celled organisms known as foraminiferans.
A chalk is a soft, friable variety of limestone consisting of poorly lithified calcareous ooze, produced by the accumulation of planktonic organisms in a pelagic (open sea) environment.
Chalk is a type of limestone. It was made by calcareous (CaCO 3) skeletons of tiny planktonic algae called coccoliths. They live in the sea in huge numbers. They make chalk (CO 2) as a by-product of their photosynthesis.
