Travertine is a form of limestone deposited by mineral springs, especially hot spring. Travertine often has a fibrous or concentricappearance and exist 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, and otherspeleothems. It is frequently used in Italy and elsewhere as a building material.