Chalk - Wikipedia Chalk is a soft, white, porous, sedimentary carbonate rock It is a form of limestone composed of the mineral calcite and originally formed under the sea by the accumulation and lithification of hard parts of organisms, mostly microscopic plankton, which had settled to the sea floor
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Chalk | Sedimentary, Limestone, Calcium Carbonate | Britannica 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: A biological limestone formed from shell debris 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
Chalk - Simple English Wikipedia, the free encyclopedia Blackboard chalk is not real chalk It is really gypsum (calcium sulfate), but people call it "chalk" People use it for drawing on hard things, because it is soft If this chalk is rubbed on something hard or rough, it will leave a mark People often write with chalk on a chalkboard or blackboard
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