Dense, banded rock composed of calcium carbonate, CaCO. Formed by rapid chemical precipitation of calcium carbonate from solution in surface and ground waters, it is a variety of limestone that has a light colour and takes a good polish. It is often used for walls and interior decorations in public buildings and as a paving stone. Travertine is mined extensively in Italy; in the U.S., Yellowstone's Mammoth Hot Springs are actively depositing travertine. It also occurs in limestone caves in the form of stalactites and stalagmites.