Calcium Carbonate – GeologyA story spanning over 200 million years of history

Calcium carbonate is formed principally from three sources: carboniferous limestone, cretaceous chalk and dolomite. The first two have the same chemical formula, but the way the materials are formed lead to very different properties.

Calcium carbonate geology is based on three principal resources: Carboniferous limestone, Cretaceous chalk and Dolomite (a mixed carbonate of calcium and magnesium).

.Sedimentation and Rock Formation

When sedimentation occurs, limestone (including chalk and marble) is formed. They typically form in two stages: loose materials come to rest in layers, and then compacted to form rock through either pressure or cementation. The formation of sedimentary rock via the physical, chemical or biological changing of sediment is known as diagenesis.

Sedimentary rocks generally form in two stages: initially loose materials are deposited in layers, and then they are consolidated to rock by pressure or cementation. The physical, chemical or biological alteration of sediments into sedimentary rock is called diagenesis.

.Rocks of Biological Origins

When the original material that forms the basis of rocks is biological in nature, you end up with limestone deposits. This is called organogenic sedimentation. Invertebrates that settle on the sea bed and over time compact, from whole and broken shells to the coccolith that measures a few thousandths of a millimetre, form limestone.

.Types of Calcium Carbonate

Chalk: when coccoliths (a type of algae that secretes lime) compact, the result is chalk, a sedimentary rock that is poorly compressed.
Dolomite: when the sedimentation process takes place with magnesium, the result is dolomitisation.
Limestone: more compact than chalk, limestone is created from the remains of microscopic animals or foraminifera and is a sedimentary rock.
Marble: marble is created when chalk or limestone are subjected to high temperature and pressure to cause recrystallisation. It is a coarse-crystal metamorphic rock.