Travertine
The word 'travertine' is derived from the Italian travertino, itself a derivation of the Latin tiburtinus meaning 'of Tibur' (now known as Tivoli, near Rome, Italy).
Travertine is a sedimentary rock formed by the chemical precipitation of calcium carbonate minerals from fresh water, typically in springs, rivers, and lakes; that is, from surface and ground waters. In the broadest sense, travertine includes deposits in both hot and cold springs, including the porous, spongy rock known as tufa, and also the cave features known as speleothems (which include stalactites and stalagmites). Calcrete, which is calcium minerals deposited as a horizon in the soil profile, is not considered a form of travertine.
Similar (but softer and extremely porous) deposits formed from ambient-temperature water are known as tufa.
Most travertine is formed by precipitation during the release of carbon dioxide (CO2) into the atmosphere. This happens through the inverse of the following reaction:
CaCO3 + CO2 + H2O = Ca 2+ + 2(HCO3)-
However, there are some travertines that are produced when precipitation is generated by capturing carbon dioxide (CO2) from the atmosphere. This happens through the following reaction:
Ca(OH)2 + CO2 s = CaCO3 + H2O
However, travertine is often defined in a narrower sense as dense rock, sometimes massive but more commonly banded or with a fibrous internal structure, deposited in hot springs. In this more narrow sense, travertine is distinct from speleothems and tufa. Travertine is sometimes also defined by its mode of origin, as rock formed by inorganic precipitation of calcium carbonate minerals onto a surface following exchange of carbon dioxide between the atmosphere and groundwater. Calcrete, lake marls, and lake reefs are excluded from this definition, but both speleothems and tufa are included.
Fresh travertines vary widely in their porosity, from about 10% to 70%. However, ancient travertines may have a porosity as low as 2% due to crystallization of secondary calcite in the original pore spaces, while some of the fresh aragonite travertine at Mammoth Hot Springs has a porosity greater than 80%. A porosity of about 50% is typical for cold spring travertine while hot spring travertines have a mean porosity of about 26%. Speleothems have low porosities of less than 15%.
Uses
Travertine is often used as a building material. It typically lacks planes of weakness, and its high porosity makes it light in weight for its strength, gives it good thermal and acoustic insulating properties, and makes it relatively easy to work. Dense travertine makes excellent decorative stone when polished.
The Romans mined deposits of travertine for building temples, monuments, aqueducts, bath complexes, and amphitheatres such as the Colosseum, the largest building in the world constructed mostly of travertine. In Italy, well-known travertine quarries exist in Tivoli and Guidonia Montecelio, where the most important quarries since Ancient Roman times can be found. The Tivoli quarries supplied the travertine from which Gian Lorenzo Bernini selected material from which to build the famous Colonnade of St. Peter's Square in Rome (colonnato di Piazza S. Pietro) in 1656–1667. Michelangelo also chose travertine as the material for the external ribs of the dome of St Peter's Basilica. Travertine from Trivoli was used in the sculpting of the majority of the Trevi Fountain in Rome during the Baroque period.
Travertine regained popularity as a building material in the Middle Ages. The central German town of Bad Langensalza (where Europe's longest castle is) has an extant medieval old town built almost entirely of local travertine. Twentieth century buildings using travertine extensively include the Sacré-Cœur Basilica in Paris, the Getty Center in Los Angeles, California, and Shell-Haus in Berlin.
Travertine is one of several natural stones that are used for paving patios and garden paths. It is sometimes known as travertine limestone or travertine marble; these are the same stone, although travertine is classified properly as a type of limestone, not marble. The stone is characterised by pitted holes and troughs in its surface. Although these troughs occur naturally, they suggest signs of considerable wear and tear over time. It can also be polished to a smooth, shiny finish, and comes in a variety of colours from grey to coral-red. Travertine is also available in tile sizes for floor installations.
Types of travertine as a building material
| Cinza |
Noce |
Romano-striato |
Rosso-Soraya |
Sunflower |
Walnut |
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ref: wikipedia
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