View source for Chemistry:Dolomite (mineral)

{{Short description|Carbonate mineral - CaMg(CO₃)₂}}
{{Infobox mineral
| name        = Dolomite
| category    = [[Chemistry:Carbonate mineral|Carbonate mineral]]s
| boxwidth    =
| boxbgcolor  =
| image       = Dolomite Luzenac.jpg
| imagesize   = 260px
| caption     = Dolomite (white) on [[Chemistry:Talc|talc]]
| formula     = CaMg(CO<sub>3</sub>)<sub>2</sub>
| IMAsymbol   = Dol<ref>{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|journal=Mineralogical Magazine|volume=85|issue=3|pages=291–320|doi=10.1180/mgm.2021.43|bibcode=2021MinM...85..291W|s2cid=235729616|doi-access=free}}</ref>  
| molweight   =
| strunz      = 5.AB.10
| system      = [[Chemistry:Trigonal|Trigonal]]
| class       = Rhombohedral ({{overline|3}}) <br/>H–M symbol: ({{overline|3}})
| symmetry    = ''R''{{overline|3}}
| unit cell   = ''a'' = 4.8012(1), <br> ''c'' = 16.002&nbsp;[Å]; ''Z''&nbsp;=&nbsp;3
| color       = White, grey to pink, reddish-white, brownish-white; colourless in transmitted light
| habit       = Tabular crystals, often with curved faces, also columnar, stalactitic, granular, massive.
| twinning    = Common as simple contact twins
| cleavage    =  3 directions of cleavage not at right angles
| fracture    = Conchoidal
| tenacity    = Brittle
| mohs        = 3.5–4.0
| luster      = Vitreous to pearly
| refractive  = ''n''<sub>ω</sub> = 1.679–1.681 <br> ''n''<sub>ε</sub> = 1.500
| opticalprop = Uniaxial (−)
| birefringence = ''δ'' = 0.179–0.181
| pleochroism =
| streak      = White
| gravity     = 2.84–2.86
| melt        =
| fusibility  =
| diagnostic  =
| solubility  = Poorly soluble in dilute [[Chemistry:Hydrochloric acid|HCl]]
| diaphaneity =
| other       = May [[Biology:Fluorescence|fluoresce]] white to pink under UV; [[Physics:Triboluminescence|triboluminescent]]. <br/>[[Chemistry:Solubility equilibrium#Dissolution with dissociation|''K''<sub>sp</sub>]] values vary between 10<sup>−19</sup> and 10<sup>−17</sup>
| references  = <ref>Deer, W. A., R. A. Howie and J. Zussman (1966) ''An Introduction to the Rock Forming Minerals'', Longman, pp. 489–493. {{ISBN|0-582-44210-9}}.</ref><ref>[http://rruff.geo.arizona.edu/doclib/hom/dolomite.pdf Dolomite] {{webarchive|url=https://web.archive.org/web/20080409113311/http://rruff.geo.arizona.edu/doclib/hom/dolomite.pdf |date=2008-04-09 }}. Handbook of Mineralogy. (PDF) . Retrieved on 2011-10-10.</ref><ref>[http://webmineral.com/data/Dolomite.shtml Dolomite] {{webarchive|url=https://web.archive.org/web/20050827120622/http://webmineral.com/data/Dolomite.shtml |date=2005-08-27 }}. Webmineral. Retrieved on 2011-10-10.</ref><ref>[http://www.mindat.org/min-1304.html Dolomite] {{webarchive|url=https://web.archive.org/web/20151118232620/http://www.mindat.org/min-1304.html |date=2015-11-18 }}. Mindat.org. Retrieved on 2011-10-10.</ref><ref>{{cite book|last1=Krauskopf|first1=Konrad Bates|last2=Bird|first2=Dennis K.|title=Introduction to geochemistry|date=1995|publisher=McGraw-Hill|location=New York|isbn=9780070358201|edition=3rd|url=https://books.google.com/books?id=9g5OAQAAIAAJ|url-status=live|archive-url=https://web.archive.org/web/20170226220112/https://books.google.com/books?id=9g5OAQAAIAAJ&dq|archive-date=2017-02-26}}</ref>
}}
[[File:Thin section microscopy Siilinjärvi 501M3 etched.jpg|thumb|upright=1.25|Dolomite and calcite look similar under a microscope, but thin sections can be etched and stained in order to identify the minerals. Photomicrograph of a thin section in cross and plane polarised light: the brighter mineral grains in the picture are dolomite, and the darker grains are calcite.]]

'''Dolomite''' ({{IPAc-en|ˈ|d|ɒ|l|.|ə|ˌ|m|aɪ|t|,_|ˈ|d|ou|.|l|ə|-}}) is an [[Chemistry:Anhydrous|anhydrous]] [[Chemistry:Carbonate mineral|carbonate mineral]] composed of [[Chemistry:Calcium|calcium]] [[Chemistry:Magnesium carbonate|magnesium carbonate]], ideally {{nowrap|CaMg(CO<sub>3</sub>)<sub>2</sub>.}} The term is also used for a sedimentary [[Earth:Carbonate rock|carbonate rock]] composed mostly of the mineral dolomite (see [[Earth:Dolomite (rock)|Dolomite (rock)]]). An alternative name sometimes used for the dolomitic rock type is dolostone. 

==History==
[[File:Faloria Cortina d'Ampezzo 12.jpg|thumb|left|Cristallo in the Dolomites mountain range near Cortina d'Ampezzo, Italy. The Dolomite Mountains were named after the mineral.]]
As stated by [[Biography:Nicolas-Théodore de Saussure|Nicolas-Théodore de Saussure]]<ref>Saussure le fils, M. de (1792): Analyse de la dolomie. Journal de Physique, vol.40, pp.161-173.</ref> the mineral dolomite was probably first described by [[Biography:Carl Linnaeus|Carl Linnaeus]] in 1768.<ref>
Linnaeus, C. (1768): Systema naturae per regnum tria naturae, secundum classes, ordines, genera, species cum characteribus & differentiis. Tomus III.   Laurentii Salvii, Holmiae, 236 p. On p.41 of this very book, Linnaeus stated (in Latin): "Marmor tardum - Marmor paticulis subimpalpabilibus album diaphanum. Hoc simile quartzo durum, distinctum quod cum aqua forti non, nisi post aliquot minuta & fero, effervescens." In translation: "Slow marble - Marble, white and transparent with barely discernable particles. This is as hard as quartz, but it is different in that it does not, unless after a few minutes, effervesce with "aqua forti"".</ref> In 1791, it was described as a rock by the French [[Earth:Natural history|naturalist]] and [[Geologist|geologist]] Déodat Gratet de Dolomieu (1750–1801), first in buildings of the old city of Rome, and later as samples collected in the Tyrolean Alps. [[Biography:Nicolas-Théodore de Saussure|Nicolas-Théodore de Saussure]] first named the mineral (after Dolomieu) in March 1792.

==Properties==
The mineral dolomite crystallizes in the [[Chemistry:Trigonal|trigonal-rhombohedral]] system. It forms white, tan, gray, or pink crystals. Dolomite is a double carbonate, having an alternating structural arrangement of calcium and magnesium ions. Unless it is in fine powder form, it does not rapidly dissolve or effervesce (fizz) in cold dilute [[Chemistry:Hydrochloric acid|hydrochloric acid]] as [[Chemistry:Calcite|calcite]] does.<ref>{{cite web|url=https://geology.com/minerals/dolomite.shtml|title=Dolomite Mineral - Uses and Properties|website=geology.com}}</ref> [[Physics:Crystal twinning|Crystal twinning]] is common.

[[Physics:Solid solution|Solid solution]] exists between dolomite, the [[Chemistry:Iron|iron]]-dominant [[Chemistry:Ankerite|ankerite]] and the [[Chemistry:Manganese|manganese]]-dominant [[Chemistry:Kutnohorite|kutnohorite]].<ref name=Klein>Klein, Cornelis and Cornelius S. Hurlbut Jr., ''Manual of Mineralogy,'' Wiley, 20th ed., p. 339-340 {{ISBN|0-471-80580-7}}</ref> Small amounts of iron in the structure give the crystals a yellow to brown tint. Manganese substitutes in the structure also up to about three percent MnO. A high manganese content gives the crystals a rosy pink color. [[Chemistry:Lead|Lead]], [[Chemistry:Zinc|zinc]], and [[Chemistry:Cobalt|cobalt]] also substitute in the structure for magnesium. The mineral dolomite is closely related to [[Chemistry:Huntite|huntite]] {{nowrap|Mg<sub>3</sub>Ca(CO<sub>3</sub>)<sub>4</sub>}}.

Because dolomite can be dissolved by slightly acidic water, areas where dolomite is an abundant rock-forming mineral are important as [[Earth:Aquifer|aquifer]]s and contribute to [[Earth:Karst|karst]] terrain formation.<ref>Kaufmann, James. [http://pubs.usgs.gov/fs/2007/3060/pdf/FS2007-3060.pdf Sinkholes] {{webarchive|url=https://web.archive.org/web/20130604050448/http://pubs.usgs.gov/fs/2007/3060/pdf/FS2007-3060.pdf |date=2013-06-04 }}. USGS Fact Sheet. Retrieved on 2013-9-10.</ref>

==Formation==
Modern dolomite formation has been found to occur under [[Earth:Hypoxia (environmental)|anaerobic]] conditions in [[Physics:Supersaturation|supersaturated]] saline [[Earth:Lagoon|lagoon]]s such as those at the Rio de Janeiro coast of {{wipe|Brazil}}, namely, Lagoa Vermelha and Brejo do Espinho. There are many other localities where modern dolomite forms, notably along [[Earth:Sabkha|sabkha]]s in the Persian Gulf,<ref name=":1">{{Cite journal|date=2017-08-01|title=Microbially catalyzed dolomite formation: From near-surface to burial|url=https://www.sciencedirect.com/science/article/abs/pii/S0012825217301885|journal=Earth-Science Reviews|language=en|volume=171|pages=558–582|doi=10.1016/j.earscirev.2017.06.015|issn=0012-8252|last1=Petrash|first1=Daniel A.|last2=Bialik|first2=Or M.|last3=Bontognali|first3=Tomaso R.R.|last4=Vasconcelos|first4=Crisógono|last5=Roberts|first5=Jennifer A.|last6=McKenzie|first6=Judith A.|last7=Konhauser|first7=Kurt O.|bibcode=2017ESRv..171..558P}}</ref> but also in sedimentary basins bearing gas hydrates<ref>{{Cite journal|last1=Snyder|first1=Glen T.|last2=Matsumoto|first2=Ryo|last3=Suzuki|first3=Yohey|last4=Kouduka|first4=Mariko|last5=Kakizaki|first5=Yoshihiro|last6=Zhang|first6=Naizhong|last7=Tomaru|first7=Hitoshi|last8=Sano|first8=Yuji|last9=Takahata|first9=Naoto|last10=Tanaka|first10=Kentaro|last11=Bowden|first11=Stephen A.|date=2020-02-05|title=Evidence in the Japan Sea of microdolomite mineralization within gas hydrate microbiomes|journal=Scientific Reports|language=en|volume=10|issue=1|pages=1876|doi=10.1038/s41598-020-58723-y|pmid=32024862|issn=2045-2322|pmc=7002378|bibcode=2020NatSR..10.1876S}}</ref> and hypersaline lakes.<ref>{{Cite journal|date=1990-05-01|title=Lacustrine dolomite—an overview of modern, Holocene, and Pleistocene occurrences|url=https://www.sciencedirect.com/science/article/abs/pii/001282529090004F|journal=Earth-Science Reviews|language=en|volume=27|issue=3|pages=221–263|doi=10.1016/0012-8252(90)90004-F|issn=0012-8252|last1=Last|first1=William M.|bibcode=1990ESRv...27..221L}}</ref> It is often thought that dolomite nucleates with the help of sulfate-reducing bacteria (e.g. ''Desulfovibrio brasiliensis''),<ref>{{cite journal|author1=Vasconcelos C. |author2=McKenzie J. A. |author3=Bernasconi S. |author4=Grujic D. |author5=Tien A. J. |year=1995|title=Microbial mediation as a possible mechanism for natural dolomite formation at low temperatures|journal= Nature |volume=337|issue=6546|pages= 220–222|doi=10.1038/377220a0|bibcode = 1995Natur.377..220V |s2cid=4371495 }}</ref> but other [[Biology:Microbial metabolism|microbial metabolism]]s have been also found to mediate in dolomite formation.<ref name=":1" /> In general, low-temperature dolomite may occur in natural supersaturated environments rich in [[Earth:Extracellular polymeric substance|extracelullar polymeric substances (EPS)]] and microbial cell surfaces.<ref name=":1" /> This is likely result from complexation of  both magnesium and calcium by [[Chemistry:Carboxylic acid|carboxylic acid]]s comprising EPS.<ref>{{cite journal|author1=Roberts, J. A. |author2=Kenward, P. A. |author3=Fowle, D. A. |author4=Goldstein, R. H. |author5=Gonzalez, L. A. |author6= Moore, D. S. |name-list-style=amp |year=1980|title=Surface chemistry allows for abiotic precipitation of dolomite at low temperature |journal= Proceedings of the National Academy of Sciences of the United States of America |volume=110|issue=36|pages=14540–5|doi=10.1073/pnas.1305403110|pmid=23964124|pmc=3767548|bibcode=2013PNAS..11014540R|doi-access=free }}</ref>

Vast deposits of dolomite are present in the geological record, but the mineral is relatively rare in modern environments. Reproducible, inorganic low-temperature syntheses of dolomite are yet to be performed. Usually, the initial inorganic precipitation of a metastable "precursor" (such as magnesium calcite) can easily be achieved. The precursor phase will theoretically change gradually into a more stable phase (such as partially ordered dolomite) during periodical intervals of dissolution and re-precipitation. The general principle governing the course of this irreversible [[Chemistry:Geochemistry|geochemical]] reaction has been coined "breaking Ostwald's step rule".<ref>Deelman, J.C. (1999): [http://www.jcdeelman.demon.nl/dolomite/files/NeuesJahrbuchMineral.pdf "Low-temperature nucleation of magnesite and dolomite"] {{webarchive|url=https://web.archive.org/web/20080409113312/http://www.jcdeelman.demon.nl/dolomite/files/NeuesJahrbuchMineral.pdf |date=2008-04-09 }}, ''Neues Jahrbuch für Mineralogie'', Monatshefte, pp. 289–302.</ref>  High diagenetic temperatures, such as those of groundwater flowing along deeply rooted fault systems affecting some sedimentary successions or deeply buried limestone rocks allocate [[Earth:Dolomitization|dolomitization]].<ref>{{Cite journal|date=2000-11-01|title=Dolomite: occurrence, evolution and economically important associations|url=https://www.sciencedirect.com/science/article/abs/pii/S0012825200000222|journal=Earth-Science Reviews|language=en|volume=52|issue=1–3|pages=1–81|doi=10.1016/S0012-8252(00)00022-2|issn=0012-8252|last1=Warren|first1=J.|bibcode=2000ESRv...52....1W}}</ref>  But the mineral is also volumetrically important in some [[Earth:Neogene|Neogene]] platforms never subjected to elevated temperatures. Under such conditions of [[Earth:Diagenesis|diagenesis]] the long-term activity of the [[Biology:Deep biosphere|deep biosphere]] could play a key role in dolomitization, since diagenetic fluids of contrasting composition are mixed as a response to [[Earth:Milankovitch cycles|Milankovitch cycles]].<ref>{{Cite journal|last1=Petrash|first1=Daniel A.|last2=Bialik|first2=Or M.|last3=Staudigel|first3=Philip T.|last4=Konhauser|first4=Kurt O.|last5=Budd|first5=David A.|title=Biogeochemical reappraisal of the freshwater–seawater mixing-zone diagenetic model|url=https://onlinelibrary.wiley.com/doi/abs/10.1111/sed.12849|journal=Sedimentology|year=2021|volume=68|issue=5|pages=1797–1830|language=en|doi=10.1111/sed.12849|s2cid=234012426|issn=1365-3091}}</ref>

A recent biotic synthetic experiment claims to have precipitated ordered dolomite when [[Biology:Anoxygenic photosynthesis|anoxygenic photosynthesis]] proceeds in the presence of manganese(II).<ref>{{Cite journal|last1=Daye|first1=Mirna|last2=Higgins|first2=John|last3=Bosak|first3=Tanja|date=2019-06-01|title=Formation of ordered dolomite in anaerobic photosynthetic biofilms|url=https://pubs.geoscienceworld.org/gsa/geology/article-abstract/47/6/509/569965/Formation-of-ordered-dolomite-in-anaerobic|journal=Geology|language=en|volume=47|issue=6|pages=509–512|doi=10.1130/G45821.1|bibcode=2019Geo....47..509D|issn=0091-7613|hdl=1721.1/126802|s2cid=146426700|hdl-access=free}}</ref> A still perplexing example of an organogenic origin is that of the reported formation of dolomite in the [[Biology:Urinary bladder|urinary bladder]] of a Dalmatian dog, possibly as the result of an illness or infection.<ref>{{cite journal|author=Mansfield, Charles F. |year=1980|bibcode=1980GeCoA..44..829M|title=A urolith of biogenic dolomite – another clue in the dolomite mystery|journal=Geochimica et Cosmochimica Acta|volume=44|issue=6|pages=829–839|doi=10.1016/0016-7037(80)90264-1}}</ref>

==Uses==
Dolomite is used as an ornamental stone, a concrete aggregate, and a source of [[Chemistry:Magnesium oxide|magnesium oxide]], as well as in the [[Chemistry:Pidgeon process|Pidgeon process]] for the production of [[Chemistry:Magnesium|magnesium]]. It is an important [[Chemistry:Petroleum|petroleum]] reservoir rock, and serves as the host rock for large strata-bound Mississippi Valley-Type (MVT) [[Earth:Ore|ore]] deposits of [[Chemistry:Base metal|base metal]]s such as [[Chemistry:Lead|lead]], [[Chemistry:Zinc|zinc]], and [[Chemistry:Copper|copper]]. Where [[Chemistry:Calcite|calcite]] [[Earth:Limestone|limestone]] is uncommon or too costly, dolomite is sometimes used in its place as a [[Engineering:Flux (metallurgy)|flux]] for the [[Engineering:Smelting|smelting]] of iron and steel. Large quantities of processed dolomite are used in the production of [[Engineering:Float glass|float glass]].

In [[Earth:Horticulture|horticulture]], dolomite and dolomitic limestone are added to soils and soilless potting mixes as a pH buffer and as a magnesium source.

Dolomite is also used as the substrate in marine (saltwater) aquariums to help buffer changes in the pH of the water.

Calcined dolomite is also used as a [[Chemistry:Catalyst|catalyst]] for destruction of [[Chemistry:Tar|tar]] in the [[Physics:Gasification|gasification]] of [[Biology:Biomass|biomass]] at high temperature.<ref>[http://www.nrel.gov/docs/fy03osti/32815.pdf A Review of the Literature on Catalytic Biomass Tar Destruction] {{webarchive|url=https://web.archive.org/web/20150204170426/http://www.nrel.gov/docs/fy03osti/32815.pdf |date=2015-02-04 }} National Renewable Energy Laboratory.</ref> Particle physics researchers like to build [[Physics:Particle detector|particle detector]]s under layers of dolomite to enable the detectors to detect the highest possible number of exotic particles. Because dolomite contains relatively minor quantities of radioactive materials, it can insulate against interference from [[Astronomy:Cosmic ray|cosmic ray]]s without adding to [[Physics:Background radiation|background radiation]] levels.<ref>[https://www.newscientist.com/blogs/shortsharpscience/2011/09/particle-quest.html Short Sharp Science: Particle quest: Hunting for Italian WIMPs underground] {{webarchive|url=https://web.archive.org/web/20170517123736/https://www.newscientist.com/blogs/shortsharpscience/2011/09/particle-quest.html |date=2017-05-17 }}. Newscientist.com (2011-09-05). Retrieved on 2011-10-10.</ref>

In addition to being an industrial mineral, dolomite is highly valued by collectors and museums when it forms large, transparent crystals. The specimens that appear in the magnesite quarry exploited in Eugui, Esteribar, Navarra (Spain) are considered among the best in the world.<ref>{{cite journal|author1=Calvo M. |author2=Sevillano, E. |year=1991|title= The Eugui quarries, Navarra, Spain |journal= The Mineralogical Record |volume=22|pages= 137–142 }}</ref>

==See also==
* {{annotated link|Earth:Dolomitization}} 
* {{annotated link|Earth:Evaporite}} 
* {{annotated link|Earth:List of minerals}} 
* {{annotated link|Earth:Main Dolomite}} 
{{Clear}}

==References==
{{Reflist|30em}}

== External links ==
{{Commons}}
{{ores}}

[[Category:Sedimentary rocks]]
[[Category:Calcium minerals]]
[[Category:Magnesium minerals]]
[[Category:Carbonate minerals]]
[[Category:Dolomite group]]
[[Category:Trigonal minerals]]
[[Category:Minerals in space group 148]]
[[Category:Luminescent minerals]]
[[Category:Industrial minerals]]

{{Sourceattribution|Dolomite (mineral)}}