Travertine is a form of limestone deposited by mineral springs and geothermal springs. It is usually characterized by having naturally occurring pits and fossils in the stone material, which is typically filled during the manufacturing process in the case of polished travertine. Some travertine stones are also available in unfilled form, lending a profound visual texture to the material. Travertine can also be polished to a smooth, shiny finish, and comes in a variety of colors from grey to brown to yellow to coral-red.