Limestone is a sedimentary rock composed primarily of calcium carbonate. Depending on the formation process limestone can be classified as an organic or chemical sedimentary rock.

Organic limestone, also called biological limestone, forms in shallow, warm marine waters from the accumulation and lithification of shells, corals and skeletal debris of sea creatures. The German Jura Beige and the English Mandale Derbyshire are great examples of sedimentary organic limestone rich in clearly distinguishable fossils.

Limestone can also form through evaporation of ground or surface water rich in calcium minerals. Direct precipitation of calcium carbonate result chemical sedimentary rocks, such as travertine and tufa.

Pure limestone is white in colour but due natural impurities it is often cream, brown, grey, blue and black in colour.

Limestone is one of the most porous natural stones. This high porosity makes it more susceptible to absorption of oils, dirt and grime than other natural stones.