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Limestone  Limestone is a sedimentary rock, mainly composed of mineral calcite. The primary source of the calcite is usually marine organisms, which settle out of the water column and are deposited on the ocean floors as pelagic ooze (but see lysocline for information on calcite dissolution). Secondary calcite may also be deposited in super-saturated meteoric waters (ground water that reaches earth's surface as precipitation), as is evidenced by the creation of stalagmites and stalactites. Limestone makes up approximately 10 percent of the total volume of all sedimentary rocks. Bands of limestone emerge from the Earth's surface in often spectacular rocky outcrops and islands. For example the Verdon Gorge in France, Malham Cove in North Yorkshire, England and the Ha Long Bay National Park in Vietnam. Karst and caves are often formed in limestone. It is quarried for roadbeds and gravel roads, building and landscape construction, and cement manufacture. Limestone is especially popular in architecture and many landmarks around the world, but especially in North American and Europe, are made primarily of the material. Limestone is readily available relatively easy to cut into blocks, or more elaborate carving. It is also long lasting and stands up well to exposure. However, it is a very heavy material making it impractical for tall buildings it is also quite expensive. Limestone was most popular in the early twentieth and late nineteenth century. Still today train stations, banks and other structures from that era are normally limestone. Limestone is used as a facade on some skyscrapers, but only thin sheets rather than solid blocks. In North America most limestone used in construction comes from Indiana. See also: marble, list of minerals, coquina, travertine, chalk, dolomite, quicklime, Solnhofen limestone, Oamaru stone cy:Calchfaen de:Kalkstein et:Lubjakivi fr:Calcaire nl:Kalksteen ja:石灰岩 pl:Wapień sv:Kalksten
Categories: Materials | Sedimentary rocks
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