Dictionary:
lime·stone (līm'stōn')
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limestone |
Britannica Concise Encyclopedia:
limestone |
For more information on limestone, visit Britannica.com.
Sci-Tech Encyclopedia:
Limestone |
A common sedimentary rock composed predominantly of carbonates of calcium and magnesium. Limestones are the most voluminous of the nonsiliciclastic sedimentary rocks. In the strict sense, limestones refer to sedimentary rocks composed of the calcium carbonate mineral calcite (CaCO3). Those rocks, dominated by the magnesium-calcium carbonate mineral dolomite [CaMg(CO3)2], are known as dolomites or dolostones. Although most limestones are similar in chemical and mineralogical composition, the complex organic and chemical origins of carbonate sediments lead to a wide range of textures and fabrics in the resulting limestones. These textures and fabrics share significant parallels with those found in siliciclastic rocks, and they are quite useful for the classification and determination of depositional environments for limestones. Limestones and dolomites are used commercially as building materials and as a source for industrial and agricultural lime. In addition, limestones and dolomites are important reservoirs for oil and gas and are the hosts for important mineral deposits, including lead, zinc, silver, and fluorite. See also Lime (industry); Ore and mineral deposits; Petroleum geology; Stone and stone products.
Most marine limestones (perhaps 90% or more) originate as calcium carbonate skeletal elements of various organisms, including both plants (marine algae such as Lithothamnion and phytoplankton such as coccoliths) and animals (such as corals, clams, snails, and oysters). The larger organisms are broken down into cobble-to-silt-sized sediments by biological processes, such as boring, browsing, and grazing, in the environment. Once formed, these sediments react to environmental processes as do their siliciclastic counterparts. See also Algae; Chalk; Depositional systems and environments; Marine sediments; Stratigraphy.
Some limestones and limestone components are formed by direct chemical precipitation from marine and meteoric waters. Most modern, tropical, marine surface water is supersaturated with respect to calcium carbonate. If carbon dioxide is removed from this water by warming, agitation, or photosynthesis, there is a tendency for calcium carbonate to be precipitated. This precipitation can take several forms: an aragonite or magnesian calcite cement, which lithifies carbonate sediment, such as the beach rock commonly found along tropical beaches; an aragonite precipitate on a moving nucleus in a high-energy environment, forming highly polished, round, sand-sized particles termed ooids; or clouds of spontaneously precipitated, clay-sized aragonite, forming on shallow carbonate platforms or in restricted bays. See also Oolite.
Finally, some limestones are formed in fresh-water environments associated with caves (speleothems, such as stalactites and stalagmites), springs (tufa and travertine), and lakes (almost always chemically precipitated fine muds of calcite, dolomite, or alkali-carbonates). See also Cave; Stalactites and stalagmites; Travertine; Tufa.
Textures and fabrics in limestones are much more difficult to interpret than in siliciclastics, because of the organic origin of most carbonate grains. While grain size distribution in siliciclastics is controlled by the flow velocity at the site of deposition, grain size distribution in carbonates may be controlled by the types of organisms present in the environment that furnishes the grains. As an example, an environment dominated by large mollusks will tend to produce a sediment characterized by coarse grain sizes, whereas a benthic foraminiferal community will tend to produce grain sizes that are much finer. Roundness in siliciclastic deposits may be used to infer transport and depositional processes. Roundness in the individual grains of a limestone, however, may reflect only the original shape of the organism or the architecture of its skeleton.
Geography Dictionary:
limestone |
A general term for a sedimentary rock which consists mainly of calcium carbonate. Limestones vary in texture; oolitic limestone consists of tiny, rounded grains, pesolitic of larger grains, whereas other limestones are of a crystalline texture. Limestones also vary in mineral content, as with dolomite and magnesian limestone, and in modes of origin. Different limestones are classified according to geological age, as in Carboniferous or Jurassic limestones. Chalk is a soft limestone.
Architecture:
limestone |
Rock of sedimentary origin composed principally of calcite or dolomite or both; used as building stone or crushed-stone aggregate or burnt to produce lime.
Columbia Encyclopedia:
limestone |
Veterinary Dictionary:
limestone |
Rock which is largely calcium carbonate, used as a livestock feed when ground. Contains 38% calcium and is used as a calcium supplement. See also dolomite.
Science Dictionary:
limestone |
Sedimentary rock formed primarily of calcium carbonate, often the skeletons of small marine organisms.
Wikipedia:
Limestone |
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This article's introduction section may not adequately summarize its contents. To comply with Wikipedia's lead section guidelines, please consider expanding the lead to provide an accessible overview of the article's key points. (September 2009) |
| Limestone | |
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| — Sedimentary Rock — | |
| Limestone cropping at São Pedro de Moel beach, Marinha Grande, Portugal | |
| Composition | |
| Calcium carbonate: inorganic crystalline calcite and/or organic calcareous material. |
Limestone is a sedimentary rock composed largely of the mineral calcite (calcium carbonate: CaCO3). Like most other sedimentary rocks, limestones are comprised of grains, however, around 80-90% of limestone grains are skeletal fragments of marine organisms such as coral or foraminifera. Other carbonate grains comprising limestones are ooids, peloids, intraclasts, and extraclasts. Some limestones do not consist of grains at all and are formed completly by the chemical precipitation of calcite or aragonite. i.e. travertine
The solubility of limestone in water and weak acid solutions leads to karst landscapes. Regions overlying limestone bedrock tend to have fewer visible groundwater sources (ponds and streams), as surface water easily drains downward through joints in the limestone. While draining, water and organic acid from the soil slowly (over thousands or millions of years) enlarges these cracks; dissolving the calcium-carbonate and carrying it away in solution. Most cave systems are through limestone bedrock.
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Limestone often contains variable amounts of silica in the form of chert (aka chalcedony, flint, jasper, etc) or siliceous skeletal fragment (sponge spicules, diatoms, radiolarins), as well as varying amounts of clay, silt and sand sized terrestrial detritus carried in by rivers. The primary source of the calcite in limestone is most commonly marine organisms. These organisms secrete shells made of aragonite or calcite and leave these shells behind after the organism dies. Some of these organisms can contruct mounds of rock known as reefs, building upon past generations. Below about 3,000 meters, water pressure and temperature causes the dissolution of calcite to increase non-linearly so that limestone typically does not form in deeper waters (see lysocline). 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.[1][2] Limestones may also form in both lacustrine and evaporite depositional environments.[3][4]
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 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[5], England; on Fårö near the Swedish island of Gotland, the Niagara Escarpment in Canada/United States, Notch Peak in Utah, the Ha Long Bay National Park in Vietnam and the hills around the Lijiang River and Guilin city in China.
The Florida Keys, islands off the south coast of Florida, are composed mainly of oolitic limestone (the Lower Keys) and the carbonate skeletons of coral reefs (the Upper Keys), which thrived in the area during interglacial periods when sea level was higher than at present.
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 Öland, 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.[6]
Limestone is very common in architecture, especially in North America and Europe. Many landmarks across the world, including the Great Pyramid and its associated Complex in Giza, Egypt, are made of limestone. So many buildings in Kingston, Canada were constructed from it that it is nicknamed the 'Limestone City'. [7] 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 late 19th and early 20th 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, is 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 (to a lesser extent) marble are reactive to acid solutions, making acid rain a significant problem to the preservation of artifacts made from this stone. 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:
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Limestone in Waitomo District, New Zealand. |
A stratigraphic section of Ordovician limestone exposed in central Tennessee, U.S. The less-resistant and thinner beds are composed of shale. Vertical lines are drill holes for explosives used during road construction. |
Etched section of a sample of fossiliferous limestone from the Kope Formation near Cincinnati, Ohio. |
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Translations:
limestone |
Français (French)
n. - calcaire
Deutsch (German)
n. - Kalkstein
Ελληνική (Greek)
n. - (γεωλ.) ασβεστόλιθος
Português (Portuguese)
n. - calcário (m) (Miner.)
Español (Spanish)
n. - piedra caliza, caliza
Svenska (Swedish)
n. - kalksten
中文(简体)(Chinese (Simplified))
石灰石
中文(繁體)(Chinese (Traditional))
n. - 石灰石
العربيه (Arabic)
(الاسم) حجر الكلس, حجر الجير
עברית (Hebrew)
n. - אבן סיד, גיר
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| freestone (in archaeology) | |
| tufa | |
| biohermite (petrology) |
| What gave limestone the name limestone? | |
| Where do you get limestone from? | |
| Were can you find limestone? |
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