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Updated Thursday, 28th September 2006

A brief description of the nature of chalk

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Chalk is a fine-grained sedimentary rock. It is usually pure white and quite soft and crumbly. It often contains rounded lumps of dark coloured flint.

Chalk Copyrighted  image Icon Copyright: The Open University

How is it formed?
Chalk is a type of limestone. It is made up of thousands of minute calcite and silica rich skeletons of tiny marine plankton, which settled through the water in warm tropical seas and accumulated on the sea floor.

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