travertine

travertine (trăv`ərtĭn, –tēn), form of massive calcium carbonate, CaCO₃, resulting from deposition by springs or rivers. It is often beautifully colored and banded as a result of the presence of iron compounds or other (e.g., organic) impurities. This material is variously known as calc-sinter and calcareous tufa and (when used for decorative purposes) as onyx marble, Mexican onyx, and Egyptian or Oriental alabaster. Travertine is generally less coarse-grained and takes a higher polish than stalactite and stalagmite, which are similar in chemical composition and origin.

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travertine

Dense, banded rock composed of calcium carbonate, CaCO₃. 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.