AskDefine | Define limestone

Dictionary Definition

limestone n : a sedimentary rock consisting mainly of calcium that was deposited by the remains of marine animals

User Contributed Dictionary

English

Noun

  1. An abundant rock of marine and fresh-water sediments; primarily composed of calcite (CaCO₃); it occurs in a variety of forms, both crystalline and amorphous.

Translations

Extensive Definition

Limestone is a sedimentary rock composed largely of the mineral calcite (calcium carbonate: CaCO3).

Description

Limestone often contains variable amounts of silica in the form of chert or flint, as well as varying amounts of clay, silt and sand as disseminations, nodules, or layers within the rock. The primary source of the calcite in limestone is most commonly marine organisms. These organisms secrete shells that settle out of the water column and are deposited on ocean floors as pelagic ooze or alternatively is conglomerated in a coral reef (see lysocline for information on calcite dissolution). Secondary calcite may also be deposited by supersaturated meteoric waters (groundwater that precipitates the material in caves). This produces speleothems such as stalagmites and stalactites. Another form taken by calcite is that of oolites (oolitic limestone) which can be recognized by its granular appearance.
Limestone makes up about 10% of the total volume of all sedimentary rocks. Limestones may also form in both lacustrine and evaporite depositional environments.
Calcite can be either dissolved by groundwater or precipitated by groundwater, depending on several factors including the water temperature, pH, and dissolved ion concentrations. Calcite exhibits an unusual characteristic called retrograde solubility in which it becomes less soluble in water as the temperature increases.
When conditions are right for precipitation, calcite forms mineral coatings that cement the existing rock grains together or it can fill fractures.
Karst topography and caves develop in carbonate rocks due to their solubility in dilute acidic groundwater. Cooling groundwater or mixing of different groundwaters will also create conditions suitable for cave formation.
Coastal limestones are often eroded by organisms which bore into the rock by various means. This process is known as bioerosion. It is most common in the tropics, and it is known throughout the fossil record (see Taylor and Wilson, 2003).
Because of impurities, such as clay, sand, organic remains, iron oxide and other materials, many limestones exhibit different colors, especially on weathered surfaces. Limestone may be crystalline, clastic, granular, or massive, depending on the method of formation. Crystals of calcite, quartz, dolomite or barite may line small cavities in the rock. Folk and Dunham classifications are used to describe limestones more precisely.
Travertine is a banded, compact variety of limestone formed along streams, particularly where there are waterfalls and around hot or cold springs. Calcium carbonate is deposited where evaporation of the water leaves a solution that is supersaturated with chemical constituents of calcite. Tufa, a porous or cellular variety of travertine, is found near waterfalls. Coquina is a poorly consolidated limestone composed of pieces of coral or shells.
During regional metamorphism that occurs during the mountain building process (orogeny) limestone recrystallizes into marble.
Limestone is a parent material of Mollisol soil group.

Limestone landscape

Limestone is partially soluble, especially in acid, and therefore forms many erosional landforms. These include limestone pavements, pot holes, cenotes, caves and gorges. Such erosion landscapes are known as karsts. Limestone is less resistant than most igneous rocks, but more resistant than most other sedimentary rocks. Limestone is therefore usually associated with hills and downland and occurs in regions with other sedimentary rocks, typically clays.
Bands of limestone emerge from the Earth's surface in often spectacular rocky outcrops and islands. Examples include the Burren in Co. Clare, Ireland; the Verdon Gorge in France; Malham Cove in North Yorkshire and the Isle of Wight, England; on Fårö near the Swedish island of Gotland, the Niagara Escarpment in Canada/USA, Notch Peak in Utah, and the Ha Long Bay National Park in Vietnam.
Unique habitats are found on alvars, extremely level expanses of limestone with thin soil mantles. The largest such expanse in Europe is the Stora Alvaret on the island of Oland, Sweden. Another area with large quantities of limestone is the island of Gotland, Sweden. Huge quarries in northwestern Europe, such as those of Mount Saint Peter (Belgium/Netherlands), extend for more than a hundred kilometers.
The world's largest limestone quarry is at Michigan Limestone and Chemical Company in Rogers City, Michigan.

Uses of limestone

Limestone is very common in architecture, especially in North America and Europe. Many landmarks across the world, including the pyramids in Egypt, are made of limestone. So many buildings in Kingston, Ontario, Canada were constructed from it that it is nicknamed the 'Limestone City'. On the island of Malta, a variety of limestone called Globigerina limestone was for a long time the only building material available, and is still very frequently used on all types of buildings and sculptures. Limestone is readily available and 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, and relatively expensive as a building material. Limestone was most popular in the early 20th and late 19th centuries. Train stations, banks and other structures from that era are normally made of limestone. Limestone is used as a facade on some skyscrapers, but only in thin plates for covering rather than solid blocks. In the United States, Indiana, most notably the Bloomington area, has long been a source of high quality quarried limestone, called Indiana limestone. Many famous buildings in London are built from Portland limestone.
Limestone was also a very popular building block in the Middle Ages in the areas where it occurred since it is hard, durable, and commonly occurs in easily accessible surface exposures. Many medieval churches and castles in Europe are made of limestone. Beer stone was a popular kind of limestone for medieval buildings in southern England.
Limestone and marble are very reactive to acid solutions, making acid rain a significant problem. Many limestone statues and building surfaces have suffered severe damage due to acid rain. Acid-based cleaning chemicals can also etch limestone, which should only be cleaned with a neutral or mild alkaline-based cleaner.
Other uses include:
  • The manufacture of quicklime (calcium oxide) and slaked lime (calcium hydroxide);
  • Cement and mortar;
  • Pulverized limestone is used as a soil conditioner to neutralize acidic soil conditions;
  • Crushed for use as aggregate—the solid base for many roads;
  • Geological formations of limestone are among the best petroleum reservoirs;
  • As a reagent in desulfurizations;
  • Glass making, in some circumstances;
  • Toothpaste;
  • Suppression of methane explosions in underground coal mines
  • Added to bread as a source of calcium

Notes

References

limestone in Arabic: حجر جيري
limestone in Aragonese: Calsinera
limestone in Min Nan: Chio̍h-hoe-giâm
limestone in Bosnian: Krečnjak
limestone in Bulgarian: Варовик
limestone in Catalan: Pedra calcària
limestone in Czech: Vápenec
limestone in Welsh: Calchfaen
limestone in German: Kalkstein
limestone in Estonian: Lubjakivi
limestone in Modern Greek (1453-): Ασβεστόλιθος
limestone in Spanish: Caliza
limestone in Esperanto: Kalkoŝtono
limestone in Basque: Kareharri
limestone in French: Calcaire
limestone in Galician: Caliza
limestone in Korean: 석회암
limestone in Croatian: Vapnenac
limestone in Indonesian: Batu kapur
limestone in Icelandic: Kalksteinn
limestone in Italian: Calcare
limestone in Hebrew: אבן גיר
limestone in Latvian: Kaļķakmens
limestone in Lithuanian: Klintis
limestone in Hungarian: Mészkő (kőzet)
limestone in Maltese: Ġebla tal-ġir
limestone in Dutch: Kalksteen
limestone in Japanese: 石灰岩
limestone in Norwegian: Kalkstein
limestone in Norwegian Nynorsk: Kalkstein
limestone in Polish: Wapień
limestone in Portuguese: Calcário
limestone in Quechua: Isku
limestone in Russian: Известняк
limestone in Simple English: Limestone
limestone in Slovak: Vápenec
limestone in Slovenian: Apnenec
limestone in Serbian: Кречњак
limestone in Finnish: Kalkkikivi
limestone in Swedish: Kalksten
limestone in Thai: หินปูน
limestone in Vietnamese: Đá vôi
limestone in Turkish: Kireç taşı
limestone in Ukrainian: Вапняк
limestone in Chinese: 石灰岩
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