Travertine TRAVERTIN is a form of massive calcium carbonate, CaCO3 resulting from deposition by springs or rivers. It is often attractively colored and striped due to the presence of iron compounds or other (e.g. organic) impurities. This material is known as calc-sintered tuff and limestone and (when used for decorative purposes) as onyx marble, Mexican onyx, and Egyptian or Oriental alabaster. Travertine generally has a less coarse grain and takes a higher polish than stalactite and stalagmite, which are similar in chemical composition and origin. Travertine, the stone of the Colosseum and St. Peter's as well as several structures in New York and Philadelphia, is not a volcanic tuff but a limestone sediment deposited on the ground by the hot springs that began flowing during the first eruptions. Albanian volcanoes. The best quality, in fact the only reliable one in Lazio, is that found between Bagni and the Sabine hills below Tivoli. Lanciani, who gave a fascinating description of the quarries there, estimated that five and a half million cubic meters of stone were extracted from the old quarry alone. And yet, due to its position beneath a grassy plain, the Romans did not discover the existence of this remarkable stone until after the mid-2nd century BC; and even after that they failed for a century to develop a system for extracting stone in a way simple enough to make its widespread use possible. In the last decades of the second century BC it replaced the peperino as the inscriptional monument for obvious reasons. Its use in large works cannot be established with certainty before the construction of the Mulvien bridge in 109,...... middle of paper ......lonade, as well as for the door jambs and the horizontal arch above the door near the floor on the Forum side. The builder therefore chose it not only for the parts requiring decoration, but also for the points of great tension, and that he knew its ability to resist wear is proven by its use for the long staircase of 66 steps which leads inside the interior. from the Forum to the Capitol. Peperino and Grotta Oscura stone are not an integral part of the masonry. Most of the vaults are made of concrete. There seems to be only one piece of marble, it is the threshold of the small door on the Forum side; a strange piece of luxury; it is Pentelic. References Frank, Tenney. Roman buildings of the Republic: an attempt to date them based on their materials. American Academy in Rome: Rome. 1924. p. 34 Travertine http://www.antalya-ws.com/english/underwat/falez.asp#