Limestone tile is made of limestone, which is a natural material composed mainly of calcium carbonate with inclusions of other minerals. It is a hard sedimentary rock formed a long time ago in warm and shallow sea waters. Limestone often contains fragments of relict shells and fish bones. It is one of the most popular building materials in the world, widely used for interior and exterior surfaces because of its durability and attractive appearance. Limestone tiles are quite soft and porous, but sturdy at the same time.