Limestone

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For other uses, see Limestone (disambiguation). Limestone_sentence_0

Limestone_table_infobox_0

LimestoneLimestone_table_caption_0
CompositionLimestone_header_cell_0_0_0

Limestone is a type of carbonate sedimentary rock. Limestone_sentence_1

It is composed mostly of the minerals and aragonite, which are different crystal forms of calcium carbonate (CaCO3). Limestone_sentence_2

A closely related rock is dolomite, which contains a high percentage of the mineral dolomite, CaMg(CO3)2. Limestone_sentence_3

In old USGS publications, dolomite was referred to as magnesian limestone, a term now reserved for magnesium-deficient dolomites or magnesium-rich limestones. Limestone_sentence_4

About 10% of sedimentary rocks are limestones. Limestone_sentence_5

The solubility of limestone in water and weak acid solutions leads to karst landscapes, in which water erodes the limestone over thousands to millions of years. Limestone_sentence_6

Most cave systems are found in limestone bedrock. Limestone_sentence_7

Limestone has numerous uses: as a building material, an essential component of concrete (Portland cement), as aggregate for the base of roads, as white pigment or filler in products such as toothpaste or paints, as a chemical feedstock for the production of lime, as a soil conditioner, and as a popular decorative addition to rock gardens. Limestone_sentence_8

Description Limestone_section_0

Like most other sedimentary rocks, most limestone is composed of grains. Limestone_sentence_9

Most grains in limestone are skeletal fragments of marine organisms such as coral or foraminifera. Limestone_sentence_10

These organisms secrete shells made of aragonite or , and leave these shells behind when they die. Limestone_sentence_11

Other carbonate grains composing limestones are ooids, peloids, and limeclasts (intraclasts and extraclasts). Limestone_sentence_12

Limestone often contains variable amounts of silica in the form of chert (chalcedony, flint, jasper, etc.) or siliceous skeletal fragment (sponge spicules, diatoms, radiolarians), and travertine (a precipitate of calcite and aragonite). Limestone_sentence_13

Secondary calcite may be deposited by supersaturated meteoric waters (groundwater that precipitates the material in caves). Limestone_sentence_14

This produces speleothems, such as stalagmites and stalactites. Limestone_sentence_15

Another form taken by calcite is oolitic limestone, which can be recognized by its granular (oolite) appearance. Limestone_sentence_16

Other limestones are primarily composed of recrystalised lime mud, and are referred to as micrite. Limestone_sentence_17

The primary source of the calcite in limestone is most commonly marine organisms. Limestone_sentence_18

Some of these organisms can construct mounds of rock known as reefs, building upon past generations. Limestone_sentence_19

Below about 3,000 meters, water pressure and temperature conditions cause the dissolution of calcite to increase nonlinearly, so limestone typically does not form in deeper waters (see lysocline). Limestone_sentence_20

Limestones may also form in lacustrine and evaporite depositional environments. Limestone_sentence_21

Calcite can be dissolved or precipitated by groundwater, depending on several factors, including the water temperature, pH, and dissolved ion concentrations. Limestone_sentence_22

Calcite exhibits an unusual characteristic called retrograde solubility, in which it becomes less soluble in water as the temperature increases. Limestone_sentence_23

Impurities (such as clay, sand, organic remains, iron oxide, and other materials) will cause limestones to exhibit different colors, especially with weathered surfaces. Limestone_sentence_24

Limestone may be crystalline, clastic, granular, or massive, depending on the method of formation. Limestone_sentence_25

Crystals of calcite, quartz, dolomite or barite may line small cavities in the rock. Limestone_sentence_26

When conditions are right for precipitation, calcite forms mineral coatings that cement the existing rock grains together, or it can fill fractures. Limestone_sentence_27

Travertine is a banded, compact variety of limestone formed along streams, particularly where there are waterfalls and around hot or cold springs. Limestone_sentence_28

Calcium carbonate is deposited where evaporation of the water leaves a solution supersaturated with the chemical constituents of calcite. Limestone_sentence_29

Tufa, a porous or cellular variety of travertine, is found near waterfalls. Limestone_sentence_30

Coquina is a poorly consolidated limestone composed of pieces of coral or shells. Limestone_sentence_31

During regional metamorphism that occurs during the mountain building process (orogeny), limestone recrystallizes into marble. Limestone_sentence_32

Limestone is a parent material of the Mollisol soil group. Limestone_sentence_33

Classification Limestone_section_1

See also: List of types of limestone Limestone_sentence_34

Two major classification schemes, the Folk and Dunham, are used for identifying the types of carbonate rocks collectively known as limestone. Limestone_sentence_35

Folk classification Limestone_section_2

Main article: Folk's carbonate classification Limestone_sentence_36

Robert L. Folk developed a classification system that places primary emphasis on the detailed composition of grains and interstitial material in carbonate rocks. Limestone_sentence_37

Based on composition, there are three main components: allochems (grains), matrix (mostly micrite), and cement (sparite). Limestone_sentence_38

The Folk system uses two-part names; the first refers to the grains and the second to the cement. Limestone_sentence_39

For example, a limestone consisting mainly of ooids, with a crystalline matrix, would be termed an oosparite. Limestone_sentence_40

It is helpful to have a petrographic microscope when using the Folk scheme, because it is easier to determine the components present in each sample. Limestone_sentence_41

Dunham classification Limestone_section_3

Main article: Dunham classification Limestone_sentence_42

Robert J. Dunham published his system for limestone in 1962. Limestone_sentence_43

It focuses on the depositional fabric of carbonate rocks. Limestone_sentence_44

Dunham divides the rocks into four main groups based on relative proportions of coarser clastic particles, based on criteria such as whether the grains were originally in mutual contact, and therefore self-supporting, or whether the rock is characterized by the presence of frame builders and algal mats. Limestone_sentence_45

Unlike the Folk scheme, Dunham deals with the original porosity of the rock. Limestone_sentence_46

The Dunham scheme is more useful for hand samples because it is based on texture, not the grains in the sample. Limestone_sentence_47

A revised classification was proposed by Wright (1992). Limestone_sentence_48

It adds some diagenetic patterns to the classification scheme. Limestone_sentence_49

Formation Limestone_section_4

The solubility of calcium carbonate (CaCO3) is controlled largely by the partial pressure of carbon dioxide (CO2) in the water. Limestone_sentence_50

This is summarized in the reaction: Limestone_sentence_51

Limestone_description_list_0

  • Limestone_item_0_0
    • CaCO3 + H2O + CO2 → Ca(aq) + 2 HCO3Limestone_item_0_1

Increases in temperature or decreases in pressure tend to reduce the partial pressure of CO2 and precipitate CaCO3. Limestone_sentence_52

Reduction in salinity also reduces the solubility of CaCO3, by several orders of magnitude for fresh water versus seawater. Limestone_sentence_53

Near-surface water of the earth's oceans are oversaturated with CaCO3 by a factor of more than six. Limestone_sentence_54

The failure of CaCO3 to precipitate out of these waters is likely due to interference by dissolved magnesium ions with nucleation of calcite crystals, the necessary first step in precipitation. Limestone_sentence_55

Although ooids may form through purely inorganic processes, the bulk of CaCO3 precipitation in the oceans is the result of biological activity. Limestone_sentence_56

Much of this takes place on carbonate platforms. Limestone_sentence_57

Limestone landscape Limestone_section_5

Main article: Karst topography Limestone_sentence_58

About 10% of all sedimentary rocks are limestones. Limestone_sentence_59

Limestone is partially soluble, especially in acid, and therefore forms many erosional landforms. Limestone_sentence_60

These include limestone pavements, pot holes, cenotes, caves and gorges. Limestone_sentence_61

Such erosion landscapes are known as karsts. Limestone_sentence_62

Limestone is less resistant than most igneous rocks, but more resistant than most other sedimentary rocks. Limestone_sentence_63

It is therefore usually associated with hills and downland, and occurs in regions with other sedimentary rocks, typically clays. Limestone_sentence_64

Karst topography and caves develop in limestone rocks due to their solubility in dilute acidic groundwater. Limestone_sentence_65

The solubility of limestone in water and weak acid solutions leads to karst landscapes. Limestone_sentence_66

Regions overlying limestone bedrock tend to have fewer visible above-ground sources (ponds and streams), as surface water easily drains downward through joints in the limestone. Limestone_sentence_67

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. Limestone_sentence_68

Most cave systems are through limestone bedrock. Limestone_sentence_69

Cooling groundwater or mixing of different groundwaters will also create conditions suitable for cave formation. Limestone_sentence_70

Coastal limestones are often eroded by organisms which bore into the rock by various means. Limestone_sentence_71

This process is known as bioerosion. Limestone_sentence_72

It is most common in the tropics, and it is known throughout the fossil record (see Taylor and Wilson, 2003). Limestone_sentence_73

Bands of limestone emerge from the Earth's surface in often spectacular rocky outcrops and islands. Limestone_sentence_74

Examples include the Rock of Gibraltar, the Burren in County Clare, Ireland; the Verdon Gorge in France; Malham Cove in North Yorkshire and the Isle of Wight, England; the Great Orme in Wales; 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. Limestone_sentence_75

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. Limestone_sentence_76

Unique habitats are found on alvars, extremely level expanses of limestone with thin soil mantles. Limestone_sentence_77

The largest such expanse in Europe is the Stora Alvaret on the island of Öland, Sweden. Limestone_sentence_78

Another area with large quantities of limestone is the island of Gotland, Sweden. Limestone_sentence_79

Huge quarries in northwestern Europe, such as those of Mount Saint Peter (Belgium/Netherlands), extend for more than a hundred kilometers. Limestone_sentence_80

The world's largest limestone quarry is at Michigan Limestone and Chemical Company in Rogers City, Michigan. Limestone_sentence_81

Uses Limestone_section_6

Limestone is very common in architecture, especially in Europe and North America. Limestone_sentence_82

Many landmarks across the world, including the Great Pyramid and its associated complex in Giza, Egypt, were made of limestone. Limestone_sentence_83

So many buildings in Kingston, Ontario, Canada were, and continue to be, constructed from it that it is nicknamed the 'Limestone City'. Limestone_sentence_84

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_sentence_85

Limestone is readily available and relatively easy to cut into blocks or more elaborate carving. Limestone_sentence_86

Ancient American sculptors valued limestone because it was easy to work and good for fine detail. Limestone_sentence_87

Going back to the Late Preclassic period (by 200–100 BCE), the Maya civilization (Ancient Mexico) created refined sculpture using limestone because of these excellent carving properties. Limestone_sentence_88

The Maya would decorate the ceilings of their sacred buildings (known as lintels) and cover the walls with carved limestone panels. Limestone_sentence_89

Carved on these sculptures were political and social stories, and this helped communicate messages of the king to his people. Limestone_sentence_90

Limestone is long-lasting and stands up well to exposure, which explains why many limestone ruins survive. Limestone_sentence_91

However, it is very heavy (density 2.6), making it impractical for tall buildings, and relatively expensive as a building material. Limestone_sentence_92

Limestone was most popular in the late 19th and early 20th centuries. Limestone_sentence_93

Train stations, banks and other structures from that era were normally made of limestone. Limestone_sentence_94

It is used as a facade on some skyscrapers, but only in thin plates for covering, rather than solid blocks. Limestone_sentence_95

In the United States, Indiana, most notably the Bloomington area, has long been a source of high-quality quarried limestone, called Indiana limestone. Limestone_sentence_96

Many famous buildings in London are built from Portland limestone. Limestone_sentence_97

Houses built in Odessa in Ukraine in the 19th century were mostly constructed from limestone and the extensive remains of the mines now form the Odessa Catacombs. Limestone_sentence_98

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. Limestone_sentence_99

Many medieval churches and castles in Europe are made of limestone. Limestone_sentence_100

Beer stone was a popular kind of limestone for medieval buildings in southern England. Limestone_sentence_101

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. Limestone_sentence_102

Many limestone statues and building surfaces have suffered severe damage due to acid rain. Limestone_sentence_103

Likewise limestone gravel has been used to protect lakes vulnerable to acid rain, acting as a pH buffering agent. Limestone_sentence_104

Acid-based cleaning chemicals can also etch limestone, which should only be cleaned with a neutral or mild alkali-based cleaner. Limestone_sentence_105

Other uses include: Limestone_sentence_106

Limestone_unordered_list_1

  • It is the raw material for the manufacture of quicklime (calcium oxide), slaked lime (calcium hydroxide), cement and mortar.Limestone_item_1_2
  • Pulverized limestone is used as a soil conditioner to neutralize acidic soils (agricultural lime).Limestone_item_1_3
  • Is crushed for use as aggregate—the solid base for many roads as well as in asphalt concrete.Limestone_item_1_4
  • Geological formations of limestone are important petroleum reservoirs;Limestone_item_1_5
  • As a reagent in flue-gas desulfurization, it reacts with sulfur dioxide for air pollution control.Limestone_item_1_6
  • Glass making, in some circumstances, uses limestone.Limestone_item_1_7
  • It is added to toothpaste, paper, plastics, paint, tiles, and other materials as both white pigment and a cheap filler.Limestone_item_1_8
  • It can suppress methane explosions in underground coal mines.Limestone_item_1_9
  • Purified, it is added to bread and cereals as a source of calcium.Limestone_item_1_10
  • Calcium levels in livestock feed are supplemented with it, such as for poultry (when ground up).Limestone_item_1_11
  • It can be used for remineralizing and increasing the alkalinity of purified water to prevent pipe corrosion and to restore essential nutrient levels.Limestone_item_1_12
  • Used in blast furnaces, limestone binds with silica and other impurities to remove them from the iron.Limestone_item_1_13

Occupational safety and health Limestone_section_7

People can be exposed to limestone in the workplace by inhalation of and eye contact with the dust. Limestone_sentence_107

United States Limestone_section_8

The Occupational Safety and Health Administration (OSHA) has set the legal limit (permissible exposure limit) for limestone exposure in the workplace as 15 mg/m total exposure and 5 mg/m respiratory exposure over an 8-hour workday. Limestone_sentence_108

The National Institute for Occupational Safety and Health (NIOSH) has set a recommended exposure limit (REL) of 10 mg/m total exposure and 5 mg/m respiratory exposure over an 8-hour workday. Limestone_sentence_109

Graffiti Limestone_section_9

Removing graffiti from weathered limestone is difficult because it is a porous and permeable material. Limestone_sentence_110

The surface is fragile so usual abrasion methods run the risk of "severe surface loss". Limestone_sentence_111

Because it is an acid-sensitive stone some cleaning agents cannot be used due to adverse effects. Limestone_sentence_112

Degradation by organisms Limestone_section_10

The cyanobacterium Hyella balani can bore through limestone; as can the green alga Eugamantia sacculata and the fungus Ostracolaba implexa. Limestone_sentence_113


Credits to the contents of this page go to the authors of the corresponding Wikipedia page: en.wikipedia.org/wiki/Limestone.