travertine

travertine , form of massive calcium carbonate, CaCO ₃ , 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.

travertine Calcium carbonate deposited by precipitation from carbonate-saturated waters, particularly from hot springs. Travertine deposits are sometimes massive, but often display a concentric or fibrous internal structure, sometimes building large, concentric, spherical masses. Travertine is also found in cave deposits in the form of stalagmites and stalactites. A porous, sponge-textured form of travertine is referred to as ‘tufa’ or ‘calc-sinter’.