travertine

A light-colored porous calcite, CaCO₃, deposited from solution in ground or surface waters and forming, among other deposits, stalactites and stalagmites.

A compact calcium carbonate used as a facing material in construction.

A white concretionary form of calcium carbonate, usually hard and semicrystalline. It is deposited from the water of springs or streams holding lime in solution. Extensive deposits exist at Tivoli, near Rome.

Any of several light, porous forms of calcite deposited from solution; found most often as stalactites and stalagmites.

A similar form of limestone used as a facing material in building.