TRAVERTINE IN ZAGREB
Travertine is a form of terrestrial limestone deposited around mineral springs, especially hot springs. It often has a fibrous or concentric appearance and exists in white, tan, cream-colored, and even rusty varieties. It is formed by a process of rapid precipitation of calcium carbonate, often at the mouth of a hot spring or in a limestone cave. In the latter, it can form stalactites, stalagmites, and other speleothems. It is frequently used in Italy and elsewhere as a building material.
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.
Travertine is often defined in a more narrow 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%. Ancient ones may have porosities 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%.
DIFFERENT COLOURS OF TRAVERTINE
Travertine needs water which contains acidic water (carbon acid) and rock containing limestone for its formation. The limestone is solved by the acidic water and the water carries it along the trail. When the water reaches the surface, then the environment changes and the lime deposits at the surface as the rock called travertine. There are some appearances of travertine formations. Tufa is formed where karstic water reaches the surface. Water H2O and carbon dioxide CO2 together construct H2CO3. The last one solves the lime out of the rocks who solves in water with Ca(HCO3)2.Ca(HCO3)2 is ten times more easy to solve in water than CaCO3.
Travertine is mainly composed of calcium carbonate. The very bright yellow and brown colour at some types are caused by the mineral limonite. Very acidic environment can cause weathering evidences in travertine. But it is also resistent against freeze.
Very often the very small holes in the travertine columns show imprints of plants which were locked in during formation of the rock. Over the time the locked-in parts of plants rotted and formed the imprints you can see today.
TYPES OF TRAVERTINE
Cannstatt travertine, Baden-Wurtemberg
Roman travertine, Italy (Tivoli, near Roma)
Tuscany travertine, Tuscany (Rapolano Terme, Sienna)
Travertine of Weimar-Ehringsdorf
Travertine of Persia, Iran, East Azerbaijan, Maragha
TASKS
1. What type of rock is travertine?
2. Describe the color and texture of travertine
3. Can you see plant footprints?
4. Are the Travertine blocks used here the same?
5. According to the information and images of the listing, what type of Travertine do you see?
TRAVERTIN U ZAGREBU
Travertin je oblik kopnenog vapnenca taloženog oko mineralnih izvora, posebno toplih izvora. Često ima vlaknast ili koncentričan izgled i postoji u bijelim, žutosmeđim, krem boje, pa čak i hrđavim varijantama. Nastaje procesom brzog taloženja kalcijevog karbonata, često na ušću vrućeg izvora ili u vapnenačkoj špilji. U potonjem može formirati stalaktite, stalagmite i druge speleoteme. Često se koristi u Italiji i drugdje kao građevinski materijal.
Travertin je sedimentna stijena nastala kemijskim taloženjem minerala kalcijevog karbonata iz slatke vode, obično u izvorima, rijekama i jezerima; to jest, iz površinskih i podzemnih voda. U najširem smislu, sedra uključuje naslage u toplim i hladnim izvorima, uključujući poroznu, spužvastu stijenu poznatu kao sedra, kao i pećinske karakteristike poznate kao speleoteme (koje uključuju stalaktite i stalagmite). Kalkret, koji su minerali kalcija taloženi kao horizont u profilu tla, ne smatra se oblikom sedre.
Travertin se često definira u užem smislu kao gusta stijena, ponekad masivna, ali češće trakasta ili s vlaknastom unutarnjom strukturom, taložena u toplim izvorima. U ovom užem smislu, sedra se razlikuje od speleotema i sedre. Travertin se ponekad definira i njegovim načinom nastanka, kao stijena nastala anorganskim taloženjem minerala kalcijevog karbonata na površinu nakon izmjene ugljičnog dioksida između atmosfere i podzemnih voda. Kalkret, jezerski lapor i jezerski grebeni isključeni su iz ove definicije, ali su uključeni i speleotemi i sedra.
Poroznost svježih travertina uvelike varira, od oko 10% do 70%. Drevni mogu imati poroznost od samo 2% zbog kristalizacije sekundarnog kalcita u izvornim prostorima pora, dok neki od svježih aragonitnih travertina u Mammoth Hot Springsu imaju poroznost veću od 80%. Poroznost od oko 50% tipična je za sedru iz hladnih izvora, dok travertini iz toplih izvora imaju prosječnu poroznost od oko 26%. Speleotemi imaju nisku poroznost manju od 15%.
RAZLIČITE BOJE TRAVERTINA
Travertinu je za nastanak potrebna voda koja sadrži kiselu vodu (ugljičnu kiselinu) i stijene koje sadrže vapnenac. Kamenac se otopi kiselom vodom i voda ga nosi stazom. Kada voda dođe do površine, tada se mijenja okoliš i vapno se taloži na površini kao stijena koja se naziva sedra. Postoje neke pojave sedrenih formacija. Sedra se formira tamo gdje krška voda dospijeva na površinu. Voda H2O i ugljikov dioksid CO2 zajedno grade H2CO3. Posljednji otapa vapno iz stijena koji se otapa u vodi s Ca(HCO3)2. Ca(HCO3)2 se deset puta lakše topi u vodi nego CaCO3.
Travertin se uglavnom sastoji od kalcijevog karbonata. Vrlo jarko žuta i smeđa boja kod nekih vrsta uzrokovana je mineralom limonitom. Vrlo kiselo okruženje može uzrokovati znakove trošenja u sedri. Ali također je otporan na smrzavanje.
Vrlo često vrlo male rupe u sedrenim stupovima pokazuju otiske biljaka koje su bile zaključane tijekom formiranja stijene. S vremenom su zaključani dijelovi biljaka istrulili i formirali otiske koje danas možete vidjeti.
VRSTE TRAVERTINA
Cannstatt travertin, Baden-Würtemberg
Rimski travertin, Italija (Tivoli, blizu Roma)
Toskanski travertin, Toskana (Rapolano Terme, Sienna)
Travertin iz Weimar-Ehringsdorfa
Travertin Perzije, Irana, Istočnog Azerbajdžana, Marage
ZADACI
1. Koja je vrsta stijene sedra?
2. Opišite boju i strukturu sedre
3. Vidite li otiske biljaka?
4. Jesu li sedreni blokovi koji se ovdje koriste isti?
5. Prema informacijama i slikama na popisu, koju vrstu travertina vidite?