Travertine

Travertine ( v. Italian travertine, Latin lapis Tiburtinus, " stone from Tivoli ") is a more or less porous limestone of light, usually yellowish to brown in color, which was chemically precipitated from cold, warm or hot freshwater springs as Quellkalk. The sources contain calcium and bicarbonate ions and carbon dioxide, the travertine itself consists almost entirely of calcium carbonate. It is a Süßwasserkalk.

Designations

Different names are used for Quellkalke both the geological jargon and in the vernacular. Tufa, travertine and travertine be used differentially or even synonymous. As travertine is called in the jargon of the tufa, which is formed by the release of CO2 from CO2 - supersaturated groundwater source. This process is referred to as chemical descaling. The names of travertine are often regional or linguistically different ( depending on the occurrence). In the southwest German cuesta precipitates are designated in caves ( speleothems ) as travertine, the recent developments, but also the results of diagenesis ( fossils ) behind cold springs as tufa ( no similarity to volcanic tuff ). In English, the names Tufa and Travertine are used, in Lower Saxony, the term Duckstein. Recent travertines are usually the abiotic, ie without the involvement of living things, if the solubility of calcium carbonate by formation of carbonate ion ( CO32 - ) is exceeded by the escape of carbon dioxide. However, the photosynthetic activity of algae or moss in the water can act on the basis of the consumption of carbon dioxide favoring. Not to the natural stone is one of the artificial stone travertine, composed of colored cement and rock debris.

Education

Water, the carbon dioxide ( CO2) present in relatively high concentrations, are also characterized by relatively high concentrations of bicarbonate ions (HCO3-) and a relatively low pH of less than five. In them, calcium ions (Ca2 ) can also be solved in a higher concentration because the solubility of calcium carbonate ( CaCO3) is not achieved because of the very low concentration of carbonate ion ( CO32 - ). Emerge such waters, and sit down with the very low CO2 content of the air back into balance or will they heated so escapes by CO2. The pH increases the concentration of bicarbonate ions from the drops, and the carbonate ion increases. If the water contains calcium ions (Ca2 ), as a result, the solubility of calcium carbonate is exceeded, and the calcium ions coincide with the carbonate ions thus formed as a calcium carbonate. The solubility of calcium carbonate ( calcite ) is at 15 ° C 0.99 · 10-8 to 0.87 at 25 ° C. · 10-8 (mol / L ) 2

Waters may be enriched by the supply of CO2 from volcanic and post-volcanic degassing with dissolved CO2 and acidified by it, and they can thus release of calcium from rocks, especially limestones from when they leaked the rocks. They become potential Travertinbildnern this way: If they are heated occur in sources to the surface and / or CO2 escapes and it falls out of calcium carbonate as travertine.

More important for the emergence of the travertines as from hot springs are "cold" sources. The water is heated at the exit to the surface generally, and the dissolved lime in the cool water falls in the immediate vicinity of the source and forms rock deposits. The presence of small admixtures of limonite travertine can be yellowish to brownish, reddish haematite through to red, often layered with different intense coloration, banded in the gate.

From some thermal springs of the oolitic limestone is deposited, it then forms a so-called " pea stone ", for example in Karlovy Vary, Czech Republic.

Occurrence

Travertine is quite widespread on the continents. The deposits are usually very limited and relatively low powerful. He needs for his deposition, the close proximity of older limestone or marble deposits, of which the carbonate is derived. Travertine are in most cases very young rocks that were formed during the Quaternary.

Known occurrences are:

• In Germany Thuringia Thuringian basin ( for example Bad Langensalza, Weimar- Ehringsdorf, Bilzingsleben ) and Jena ( Pennickental )
• Baden- Wuerttemberg: Stuttgart at the Cannstatt Travertine in Cannstatt near Stuttgart and on or to the Swabian Alb ( former mining areas: Gönninger valley (upper valley of the Wiesaz ), Bad Urach )
• Lower Saxony: the ridge Elm in Braunschweig as Duckstein ( this rock gives a beer its name, the Duckstein beer)
• Bavaria: widespread in the foothills of the Alps ( center: Polling ( near Weilheim ) ) as well as the occurring mainly on the Franconian Alb Stone gutters

• Austria: Tuff Lingenau in the Bregenzerwald
• Czech Republic: aragonite deposits of Carlsbad, which has already been described by Johann Wolfgang von Goethe.
• Italy: in the area of Tivoli ( from here are building blocks for the Colosseum and St. Peter's Church in Rome); also in Alcamo ( Sicily) and in Tuscany
• France: in the Auvergne
• Croatia in the Plitvice Lakes National Park,
• Bulgaria: in Russian
• Slovak Republic: in Spišské Podhradie and in Vyšné Ružbachy

• Turkey: at Pamukkale, Çankırı ( province ) and Kayseri ( province )
• Armenia: Abovyan at
• China: Jiuzhaigou
• USA: Mammoth Hot Springs in Yellowstone National Park ( Wyoming), Mono Lake

Recent Travertinbildung occurs in areas with volcanic activity or post-volcanic CO2 degassing, especially where high tempered waters occur. Examples of such Travertinbildung are Tuscany, Italy; Pamukkale, Turkey or the Mammoth Hot Springs, Yellowstone National Park, Wyoming, USA.

Travertine terraces of Mammoth Hot Springs, Yellowstone National Park, Wyoming, USA

Muehlhaeuser Marienkirche in travertine

Built the largest castle complex in Central Europe, the Spis Castle, was made ​​of travertine deposit the near

Properties and Uses

Travertine is the most porous and riddled with cavities. Often it includes in its formation plants and plant parts which are then decomposed. In the resulting cavities often still show the external structure of the plant parts. Does then the lime precipitation still on, so the cavities can be under certain circumstances still closed, and the travertine is solid and easy to work. Travertine is easy to break in its natural occurrence and sawing. Fixed travertine has a density of about 2.40 g / cc and a compressive strength of about 50 megapascals, it is suitable for grinding and polishing, and thus as a building block for decoration ( walls, door and window frames ) and for building improvements. Travertine are frost resistant, despite their high water absorption of 0.3 to 3.0 mass percent. Due to the currently prevailing acidic environmental conditions, the surface is weathered relatively quickly. Travertine, which are particularly dense, can be polished. This also applies to all Travertine, if they are sawed with the bearing and polished. On exterior fades a polish in short periods of time and there is a dull patina that has strong appeal.

In construction, travertine is used as natural stone and for decoration. He is considered porous or primed.

Despite its relatively low strength travertine was because of its low density ( light weight ) and estimated in earlier times because of the ease of machining, such as churches and city walls. Travertine has been used mainly regional to rich deposits around the block. So you meet in the central Thuringia today in almost every city churches, city walls or other buildings made ​​of this material. Highest travertine building in Germany is the Market Church St. Boniface ( Bad Langensalza ) with 81 m high bell tower. In Rome, are the pillars of St. Peter's Square from Roman travertine, which was broken in Tivoli.

From Roman builders Travertinsorten were often used, depending on the availability of the basic masonry of buildings, because its open porosity results in a high evaporation surface and thereby the base area was permanently drained naturally.

Types of natural stone

• Germany Cannstatt Travertine ( Bad Cannstatt, Baden- Württemberg)
• Langensalzaer travertine ( Bad Langensalza, Thuringia )
• Gauinger travertine ( Gauingen, Baden- Württemberg)

• Roman Travertine (Italy, Tivoli near Rome)
• Travertine Tuscany (Tuscany, Italy)

• Hanácký travertine ( at Tučín, Moravia, Czech Republic), removal set
• Üröm ( in Budapest, Hungary)
• Spis ( at Spišské Podhradie, Slovak Republic )
• Denizli Yellow (Anatolia, Turkey) several varieties
• Persian travertine (Iran ), various colors

Roman travertine, Italy ( Tivoli near Rome)

Travertine Tuscany ( Rapollano at Siena)

Gerdoo'i travertine (Iran)