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Encyclopedia > Calcite
Doubly refracting Calcite from Iceberg claim, Dixon, New Mexico. This 35 pound (16 kg) crystal, on display at the National Museum of Natural History, is one of the largest single crystals in the United States.
Doubly refracting Calcite from Iceberg claim, Dixon, New Mexico. This 35 pound (16 kg) crystal, on display at the National Museum of Natural History, is one of the largest single crystals in the United States.
The unit cell of calcite
The unit cell of calcite

The carbonate mineral, calcite, is a chemical or biochemical calcium carbonate corresponding to the formula CaCO3 and is one of the most widely distributed minerals on the Earth's surface. It is a common constituent of sedimentary rocks, limestone in particular. It is also the primary mineral in metamorphic marble. It also occurs as a vein mineral in deposits from hot springs, and also occurs in caverns as stalactites and stalagmites. Calcite is often the primary constituent of the shells of marine organisms, e.g., plankton (such as coccoliths and planktic foraminifera), the hard parts of red algae, some sponges, brachiopoda, echinoderms, most bryozoa, and parts of the shells of some bivalves, such as oysters and rudists). Calcite represents the stable form of calcium carbonate; aragonite will change to calcite at 470°C, and vaterite, or μ-CaCO3, is less stable still. Image File history File linksMetadata Download high resolution version (1492x1824, 498 KB) Summary Large crystal of Calcite on display at the National Museum of Natural History in Washington, DC. Licensing I, the creator of this work, hereby release it into the public domain. ... Image File history File linksMetadata Download high resolution version (1492x1824, 498 KB) Summary Large crystal of Calcite on display at the National Museum of Natural History in Washington, DC. Licensing I, the creator of this work, hereby release it into the public domain. ... Inside the National Museum of Natural History, underneath the rotunda. ... Image File history File links Download high-resolution version (764x1100, 341 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Calcite ... Image File history File links Download high-resolution version (764x1100, 341 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Calcite ... Enargite crystals In mineralogy and crystallography, a crystal structure is a unique arrangement of atoms in a crystal. ... Wikipedia does not yet have an article with this exact name. ... Calcium carbonate is a chemical compound, with the chemical formula CaCO3. ... This article is about Earth as a planet. ... Two types of sedimentary rock: limey shale overlaid by limestone. ... For other uses, see Limestone (disambiguation). ... Quartzite, a form of metamorphic rock, from the Museum of Geology at University of Tartu collection. ... For other uses, see Marble (disambiguation). ... In geology, a vein is a finite volume within a rock, having a distinct shape, filled with crystals of one or more minerals, which were precipitated from an (aqueous) fluid. ... Green Dragon Spring at Norris Geyser A hot spring is a place where warm or hot groundwater issues from the ground on a regular basis for at least a predictable part of the year, and is significantly above the ambient ground temperature (which is usually around 55~57 F or... Alternate meanings: Cave (disambiguation) This article is about natural caves; for artificial caves used as dwellings, such as those in north China, see yaodong. ... Water droplet coming out of the central canal of a stalactite A stalactite (Greek stalaktites, (Σταλακτίτης), from the word for drip and meaning that which drips) is a type of speleothem(secondary mineral) that hangs from the ceiling or wall of limestone caves. ... Water droplet coming out of the central canal of a stalactite A stalactite (Greek stalaktites, (Σταλακτίτης), from the word for drip and meaning that which drips) is a type of speleothem(secondary mineral) that hangs from the ceiling or wall of limestone caves. ... For the SpongeBob SquarePants character, see Sheldon J. Plankton. ... Coccoliths are the individual plates formed by coccolithophores such as Emiliana huxleyi1, and arranged around them in a coccosphere. ... Orders Allogromiida Carterinida Fusulinida - extinct Globigerinida Involutinida - extinct Lagenida Miliolida Robertinida Rotaliida Silicoloculinida Spirillinida Textulariida incertae sedis    Xenophyophorea    Reticulomyxa The Foraminifera, or forams for short, are a large group of amoeboid protists with reticulating pseudopods, fine strands that branch and merge to form a dynamic net. ... Algae have conventionally been regarded as simple plants within the study of botany. ... Classes Calcarea Hexactinellida Demospongiae The sponges or poriferans (from Latin porus pore and ferre to bear) are animals of the phylum Porifera. ... Diversity About 4000 genera Subphyla and classes See Classification Brachiopods (from Latin bracchium, arm + New Latin -poda, foot) are a nearly extinct, small phylum of benthic invertebrates. ... Classes Subphylum Homalozoa Gill & Caster, 1960 Class Homostelea Class Homoiostelea Class Stylophora Gill & Caster, 1960 Class Ctenocystoidea Robison & Sprinkle, 1969 Subphylum Crinozoa Class Eocrinoidea Jaekel, 1899 Class Paracrinoidea Regnéll, 1945 Class Cystoidea von Buch, 1846 Class Blastoidea Class Crinoidea Subphylum Asterozoa Class Ophiuroidea Class Asteroidea Subphylum Echinozoa Helicoplacoidea †  ?Arkarua... Classes Stenolaemata Gymnolaemata Phylactolaemata Bryozoans are tiny colonial animals that generally build stony skeletons of calcium carbonate, superficially similar to coral. ... Subclasses Anomalosdesmata Cryptodonta Heterodonta Paleoheterodonta Palaeotaxodonta Pteriomorphia and see text Mussels in the intertidal zone in Cornwall, England. ... For other uses, see Oyster (disambiguation). ... Rudists are a group of bivalves that peaked in abundance and diversity during the late Mesozoic era, particuarly in the Cretaceous period, at the end of which they became extinct. ... Aragonite Aragonite is a polymorph of the mineral calcite, both having the chemical composition CaCO3. ... Vaterite (CaCO3) is a mineral and polymorph of aragonite and calcite. ...

Contents

Properties

fossil shell with calcite crystals
fossil shell with calcite crystals

Calcite crystals are trigonal-rhombohedral, though actual calcite rhombohedra are rare as natural crystals. However, they show a remarkable variety of habits including acute to obtuse rhombohedra, tabular forms, prisms, or various scalenohedra. Calcite exhibits several twinning types adding to the variety of observed forms. It may occur as fibrous, granular, lamellar, or compact. Cleavage is usually in three directions parallel to the rhombohedron form. Its fracture is conchoidal, but difficult to obtain. Image File history File links Size of this preview: 800 × 582 pixelsFull resolution (2500 × 1818 pixel, file size: 2. ... Image File history File links Size of this preview: 800 × 582 pixelsFull resolution (2500 × 1818 pixel, file size: 2. ... For other uses, see Fossil (disambiguation). ... Look up shell in Wiktionary, the free dictionary. ... For other uses, see Crystal (disambiguation). ... For other uses, see Crystal (disambiguation). ... In crystallography, the rhombohedral (or trigonal) crystal system is one of the seven lattice point groups. ... It has been suggested that twin boundary be merged into this article or section. ...


It has a Mohs hardness of 3, a specific gravity of 2.72, and its luster is vitreous in crystallized varieties. Color is white or none, though shades of gray, red, yellow, green, blue, violet, brown, or even black can occur when the mineral is charged with impurities. Mohs scale of mineral hardness characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer. ... Relative density (also known as specific gravity) is a measure of the density of a material. ...


Calcite is transparent to opaque and may occasionally show phosphorescence or fluorescence. It is perhaps best known because of its power to produce strong double refraction of light, such that objects viewed through a clear piece of calcite appear doubled in all of their parts—a phenomenon first described by Rasmus Bartholin. A beautifully transparent variety used for optical purposes comes from Iceland, called Iceland spar. Acute scalenohedral crystals are sometimes referred to as "dogtooth spar". Phosphorescent powder under visible light, ultraviolet light, and total darkness. ... Fluorescence induced by exposure to ultraviolet light in vials containing various sized Cadmium selenide (CdSe) quantum dots. ... A calcite crystal laid upon a paper with some letters showing the double refraction Birefringence, or double refraction, is the division of a ray of light into two rays (the ordinary ray and the extraordinary ray) when it passes through certain types of material, such as calcite crystals, depending on... Rasmus Bartholin (Latinized Erasmus Bartholinus; August 13, 1625 - November 4, 1698) was a Danish scientist and physician. ... Calcite from Brushy Creek Mine, Missouri, USA. The mineral calcite is a carbonate of calcium corresponding to the formula CaCO3 and is one of the most widely distributed minerals on the Earths surface. ...


Single calcite crystals display an optical property called birefringence. The birefringent effect (using calcite) was first described by the Danish scientist Rasmus Bartholin in 1669. At a wavelength of ~590 nm calcite has ordinary and extraordinary refractive indices of 1.658 and 1.486, respectively [1]. A calcite crystal laid upon a paper with some letters showing the double refraction Birefringence, or double refraction, is the decomposition of a ray of light into two rays (the ordinary ray and the extraordinary ray) when it passes through certain types of material, such as calcite crystals, depending on... Rasmus Bartholin (Latinized Erasmus Bartholinus; August 13, 1625 - November 4, 1698) was a Danish scientist and physician. ... // Events Samuel Pepys stopped writing his diary. ... The refractive index (or index of refraction) of a medium is a measure for how much the speed of light (or other waves such as sound waves) is reduced inside the medium. ...


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. When conditions are right for dissolution, the removal of calcite can dramatically increase the porosity and permeability of the rock, and if it continues for a long period of time may result in the formation of caverns. Solvation is the attraction and association of molecules of a solvent with molecules or ions of a solute. ... Acidity is a controversial novelette written for the popular South Asian website Chowk. ... This article is about the electrically charged particle. ... Porosity is a measure of the void spaces in a material, and is measured as a fraction, between 0–1, or as a percentage between 0–100%. The term porosity is used in multiple fields including manufacturing, earth sciences and construction. ... Permeability has several meanings: In electromagnetism, permeability is the degree of magnetisation of a material in response to a magnetic field. ... Alternate meanings: Cave (disambiguation) The outside world viewed from a cave A cave is a natural underground void. ...


"Calcite Seas" existed in Earth history when the primary inorganic precipitate of calcium carbonate in marine waters was low-magnesium calcite (lmc), as opposed to the aragonite and high-magnesium calcite (hmc) precipitated today. Calcite Seas alternated with Aragonite Seas over the Phanerozoic, being most prominent in the Ordovician and Jurassic. Petrographic evidence for these calcite sea conditions consists of calcitic ooids, lmc cements, and rapid early seafloor aragonite dissolution (Palmer and Wilson, 2004). The evolution of marine organisms with calcium carbonate shells may have been affected by the calcite and aragonite sea cycle (Harper et al., 1997). Aragonite Aragonite is a polymorph of the mineral calcite, both having the chemical composition CaCO3. ... Artist impression of the Ordovician Sea. ... The Jurassic Period is a major unit of the geologic timescale that extends from about 199. ... Thin-section of calcitic ooids from the Carmel Formation, Middle Jurassic, of southern Utah, USA. The largest is 1. ...


Calcite In Literature

A form of calcite, Iceland spar, plays a critical role in the plot of Against the Day by Thomas Pynchon. The same form is referred to in The Amber Spyglass by Philip Pullman as it has very similar properties to a mineral found in that story. Calcite from Brushy Creek Mine, Missouri, USA. The mineral calcite is a carbonate of calcium corresponding to the formula CaCO3 and is one of the most widely distributed minerals on the Earths surface. ... Against the Day, a novel by Thomas Pynchon, first appeared in the United States on November 21, 2006. ... Thomas Ruggles Pynchon, Jr. ... The Amber Spyglass is the third and final novel in the His Dark Materials series, written by British novelist Philip Pullman, and published in 2000. ... Philip Pullman CBE (born October 19, 1946) is an English writer. ...


See also

Wikisource has the text of the 1911 Encyclopædia Britannica article Calcite.

Image File history File links Wikisource-logo. ... The original Wikisource logo. ... Encyclopædia Britannica, the eleventh edition The Encyclopædia Britannica Eleventh Edition (1910–1911) is perhaps the most famous edition of the Encyclopædia Britannica. ... Monohydrocalcite is a mineral that is a hydrous form of calcium carbonate, CaCO3. ... Ikaite is the mineral name for the hexahydrate of calcium carbonate, CaCO3·6H2O. Ikaite is colorless when pure. ... Gem animals. ... The lysocline is a term used in geology, geochemistry and marine biology to denote the depth in the ocean below which the rate of dissolution of calcite increases dramatically. ... Change in sea surface pH caused by anthropogenic CO2 between the 1700s and the 1990s Ocean acidification is the name given to the ongoing decrease in the pH of the Earths oceans, caused by their uptake of anthropogenic carbon dioxide from the atmosphere. ...

References

Harper, E.M. , Palmer, T.J. and Alphey, J.R. 1997. Evolutionary response by bivalves to changing Phanerozoic sea-water chemistry. Geological Magazine 134: 403-407.


Palmer, T.J. and Wilson, M.A. 2004. Calcite precipitation and dissolution of biogenic aragonite in shallow Ordovician calcite seas. Lethaia 37: 417-427. [2]


Further reading

  • Schmittner Karl-Erich and Giresse Pierre, 1999. Micro-environmental controls on biomineralization: superficial processes of apatite and calcite precipitation in Quaternary soils, Roussillon, France. Sedimentology 46/3: 463-476.

External links

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Calcite

  Results from FactBites:
 
Calcite - LoveToKnow 1911 (1740 words)
An opaque calcite of a grass-green colour, occurring as large cleavage masses in central India and known as hislopite, owes its colour to enclosed "greenearth" (glauconite and celadonite).
Optically, calcite is uniaxial with negative bi-refringence, the index of refraction for the ordinary ray being greater than for the extraordinary ray; for sodium-light the former is 1.6585 and the latter 1.4862.
The wide distribution, under various conditions, of crystallized calcite is readily explained by the solubility of calcium carbonate in water containing carbon dioxide, and the ease with which the material is again deposited in the crystallized state when the carbon dioxide is liberated by evaporation.
calcite. The Columbia Encyclopedia, Sixth Edition. 2001-05 (226 words)
Calcite also occurs in a number of massive forms, in which it may be coarsely to finely granular (as in marble), compact (as in limestone), powdery (as in chalk), or fibrous.
Millions of tons of calcite, in the form of limestone and marble, are mined annually.
Besides its use as a building stone, it is the raw material for quicklime and cement, and is used extensively as a flux in smelting and as a soil conditioner.
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