Limestone is a sedimentary rock. It is a combination of many different fossils, calcium carbonate and or microscopic shells. Pure limestone is white in colour. Due to impurities, such as clay, sand, organic remnants, iron oxide and other materials, many limestones display different colours.

Limestone has enjoyed a successful history in exterior applications, and some of the most prominent government and financial institutions worldwide proudly display limestone as their exterior cladding.