Travertine (/ˈtrævərˌtiːn/ TRA-vər-teen) is a form of limestone, especially hot springs. Travertine often has a fibrous or concentric appearance and exists in white, tan, cream-colored, and even rusty varieties. It is formed by a process of rapid precipitation of calcium carbonate , often at the mouth of a hot spring or in a limestone cave. In the latter, it can form stalactites , stalagmites. It is frequently used in Italy and elsewhere as a building material.
Travertine is a terrestrial sedimentary rock , formed by the precipitation of carbonate minerals from solution in ground and surface waters, or geothermally heated hot-springs Similar (but softer and extremely porous) deposits formed from ambient-temperature water are known as tufa.