Limestone

Limestone is a sedimentary rock composed mainly of calcium carbonate (CaCO3). It is formed underwater water and so often contains fossils of coral and shells, and other organisms that contributed to its formation. Its grain structure is often formed of the fragments of fossilised animal shells.

Quarried limestone has many uses beyond building stone, including providing the feedstock for lime used in cement and hempcrete, glass making, agriculture (fertiliser) and as a pigment. There are several other varieties, too. Travertine, a type of terrestrial limestone, is formed from deposits around rivers and mineral springs (stalactites and stalagmites, for example). Coquina is a type of soft limestone formed almost exclusively from fossilised shells cemented together.