The BCCF - for information about calcium carbonate

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Calcium Carbonate

The World's Most Versatile Mineral

Calcium Carbonate Glossary


Chalk is a poorly compacted sedimentary rock predominately composed of compacted coccoliths (a lime-secreting algae).


Formed as limestone (see below) but the sedimentation process occurs in the presence of magnesium resulting in a dolomitisation process.


Limestone is also a sedimentary rock, but it is more compacted than chalk. It is formed from the remains of microscopic animals or foraminifera.


Marble is a coarse-crystalline, metamorphic rock, which is formed when chalk or limestone are recrystallised under conditions of high temperature and pressure.

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Chalk geology

A story of the Cretaceous period

Chalk is a poorly compacted sedimentary rock, whose diagenesis is incomplete. The sediments from which chalk originates are predominately composed of compacted coccoliths (a lime-secreting algae).

Formation of chalk by minor compaction and land folding

Minor compaction by later sediments becoming harder with formation of flints. (Source: Imerys Performance Minerals)

Chalk is a soft, white, porous form of limestone composed of the mineral calcite and maybe yellowish, grey or white in colour. Chalk is obtained from numerous sites along the European chalk belt - from the UK through France all the way to the island of Rügen in north Germany.

The major chalk producing regions in the UK are centred on the high quality chalk deposits found in Humberside, Cambridgeshire/Suffolk and Wiltshire. These deposits were laid down during the Cretaceous period between 70 and 120 million years ago.

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