A revised classification was proposed by Wright (1992). It adds some diagenetic patterns to the classification scheme. [38] Other descriptive terms Limestone often contains variable amounts of silica in the form of chert or siliceous skeletal fragments (such as sponge spicules, diatoms, or radiolarians). [12] Fossils are also common in limestone. [3] Near-surface water of the earth's oceans are oversaturated with CaCO 3 by a factor of more than six. [43] The failure of CaCO 3 to rapidly 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. Precipitation of aragonite may be suppressed by the presence of naturally occurring organic phosphates in the water. Although ooids likely form through purely inorganic processes, the bulk of CaCO 3 precipitation in the oceans is the result of biological activity. [44] Much of this takes place on carbonate platforms.

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Silicification occurs early in diagenesis, at low pH and temperature, and contributes to fossil preservation. [50] Silicification takes place through the reaction: [50] CaCO 3 + H 2 O + CO 2 + H 4 SiO 4 ⟶ SiO 2 + Ca 2 + + 2 HCO 3 − + 2 H 2 O {\displaystyle {\ce {CaCO3 + H2O + CO2 + H4SiO4 -> SiO2 + Ca Limestone is composed mostly of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate ( CaCO 3). Dolomite, CaMg(CO 3) 2, is an uncommon mineral in limestone, and siderite or other carbonate minerals are rare. However, the calcite in limestone often contains a few percent of magnesium. Calcite in limestone is divided into low-magnesium and high-magnesium calcite, with the dividing line placed at a composition of 4% magnesium. High-magnesium calcite retains the calcite mineral structure, which is distinct from dolomite. Aragonite does not usually contain significant magnesium. [8] Most limestone is otherwise chemically fairly pure, with clastic sediments (mainly fine-grained quartz and clay minerals) making up less than 5% [9] to 10% [10] of the composition. Organic matter typically makes up around 0.2% of a limestone and rarely exceeds 1%. [11] Croddy, Eric (2002). Chemical and biological warfare: a comprehensive survey for the concerned citizen. Springer. p.128. ISBN 0-387-95076-1. Fiquet, G.; Richet, P.; Montagnac, G. (Dec 1999). "High-temperature thermal expansion of lime, periclase, corundum and spinel". Physics and Chemistry of Minerals. 27 (2): 103–111. Bibcode: 1999PCM....27..103F. doi: 10.1007/s002690050246. S2CID 93706828 . Retrieved 9 February 2023. a b Haynes, William M., ed. (2011). CRC Handbook of Chemistry and Physics (92nded.). Boca Raton, FL: CRC Press. p.4.55. ISBN 1-4398-5511-0.Connelly, Ashley Nicole (May 2012) Analysis and Interpretation of Neolithic Near Eastern Mortuary Rituals from a Community-Based Perspective. Baylor University Thesis, Texas Limestone outcrops are recognized in the field by their softness (calcite and aragonite both have a Mohs hardness of less than 4, well below common silicate minerals) and because limestone bubbles vigorously when a drop of dilute hydrochloric acid is dropped on it. Dolomite is also soft but reacts only feebly with dilute hydrochloric acid, and it usually weathers to a characteristic dull yellow-brown color due to the presence of ferrous iron. This is released and oxidized as the dolomite weathers. [9] Impurities (such as clay, sand, organic remains, iron oxide, and other materials) will cause limestones to exhibit different colors, especially with weathered surfaces. Peloids are structureless grains of microcrystalline carbonate likely produced by a variety of processes. [22] Many are thought to be fecal pellets produced by marine organisms. Others may be produced by endolithic (boring) algae [23] or other microorganisms [24] or through breakdown of mollusc shells. [25] They are difficult to see in a limestone sample except in thin section and are less common in ancient limestones, possibly because compaction of carbonate sediments disrupts them. [23]

limestone powder on the properties of alkali Effect of limestone powder on the properties of alkali

Limestone forms when calcite or aragonite precipitate out of water containing dissolved calcium, which can take place through both biological and nonbiological processes. [41] The solubility of calcium carbonate ( CaCO 3) is controlled largely by the amount of dissolved carbon dioxide ( CO 2) in the water. This is summarized in the reaction:Oncoliths resemble ooids but show a radial rather than layered internal structure, indicating that they were formed by algae in a normal marine environment. [20]

Limestone - Wikipedia

Adrienne Mayor (2005), "Ancient Warfare and Toxicology", in Philip Wexler (ed.), Encyclopedia of Toxicology, vol.4 (2nded.), Elsevier, pp.117–121, ISBN 0-12-745354-7

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a b Zumdahl, Steven S. (2009). Chemical Principles 6th Ed. Houghton Mifflin Company. p.A21. ISBN 978-0-618-94690-7. In 80 BC, the Roman general Sertorius deployed choking clouds of caustic lime powder to defeat the Characitani of Hispania, who had taken refuge in inaccessible caves. [23] A similar dust was used in China to quell an armed peasant revolt in 178 AD, when lime chariots equipped with bellows blew limestone powder into the crowds. [24] Kumar, Gupta Sudhir; Ramakrishnan, Anushuya; Hung, Yung-Tse (2007), Wang, Lawrence K.; Hung, Yung-Tse; Shammas, Nazih K. (eds.), "Lime Calcination", Advanced Physicochemical Treatment Technologies, Handbook of Environmental Engineering, Totowa, NJ: Humana Press, vol.5, pp.611–633, doi: 10.1007/978-1-59745-173-4_14, ISBN 978-1-58829-860-7 , retrieved 2022-07-26

Young boy, 7, dies minutes after playing with common building

a b c d e f Tony Oates (2007), "Lime and Limestone", Ullmann's Encyclopedia of Industrial Chemistry (7thed.), Wiley, pp.1–32, doi: 10.1002/14356007.a15_317, ISBN 978-3527306732

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Chemical or power production: Solid sprays or slurries of calcium oxide can be used to remove sulfur dioxide from exhaust streams in a process called flue-gas desulfurization.