Limestone is sedimentary rock that is formed in oceans, lakes and seas, consisting of shells and sea creatures that have settled to the bottom. Calcium in this sediment combines with carbon dioxide in the water to form calcium carbonate, which is the basic structure of all limestone and marble.

Limestone comes in soft beiges and tans, either polished or honed, and is used in bathrooms, fireplaces, counters and lightly-traveled flooring where a casual or informal look is desired. Like any stone, limestone should be sealed with a penetrating sealer to prevent stains from penetrating into the stone.