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.
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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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Geology toolkit
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Discover the unique landscape of the British Isles with our interactive Geology Toolkit, featuring a geology timeline, rock analyser, rock cycle, landscape features and safety... Read more : Geology toolkit
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