GEORGE BERNARD / SCIENCE PHOTO LIBRARY GEORGE BERNARD / SCIENCE PHOTO LIBRARY
Calcareous tufa. Cut surface of calcareous tufa, a type of sedimentary rock formed from crusty layers of calcium carbonate (CaCO3) deposited by hot springs. Tufa is a soft and porous rock which is easily broken. A denser variety called travertine is extensively mined in Italy and used to make or- namental table tops, paving stones and building facades. This sample of rock is from Italy. Magnification x0.25 at 35mm size.
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