{{Short description|Carbonate mineral (CaMg(CO3)2)}} {{For|the rock|Dolomite (rock)}} {{Lead too short|date=July 2023}} {{Infobox mineral | name = Dolomite | category = Carbonate minerals | boxwidth = | boxbgcolor = | image = Dolomite Luzenac.jpg | caption = Dolomite (white) on 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 = 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 [Å]; ''Z'' = 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 HCl | diaphaneity = | other = May fluoresce white to pink under UV; triboluminescent. <br/>''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>{{cite web |url= http://webmineral.com/data/Dolomite.shtml |title= Dolomite |publisher= webmineral |accessdate= 12 March 2024 |archive-date= 2005-08-27 |archive-url= https://web.archive.org/web/20050827120622/http://webmineral.com/data/Dolomite.shtml |url-status= dead }}</ref><ref>{{cite web |url= http://www.mindat.org/min-1304.html |title= Dolomite |publisher= mindat.org |accessdate= 12 March 2024 |archive-date= 2015-11-18 |archive-url= https://web.archive.org/web/20151118232620/http://www.mindat.org/min-1304.html |url-status= dead }}. 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 anhydrous carbonate mineral composed of calcium magnesium carbonate, ideally {{nowrap|CaMg(CO<sub>3</sub>)<sub>2</sub>.}} The term is also used for a sedimentary carbonate rock composed mostly of the mineral dolomite (see 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 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 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 naturalist and 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. Nicolas-Théodore de Saussure first named the mineral (after Dolomieu) in March 1792.
==Properties== The mineral dolomite crystallizes in the 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 hydrochloric acid as calcite does.<ref>{{cite web|url=https://geology.com/minerals/dolomite.shtml|title=Dolomite Mineral - Uses and Properties|website=geology.com}}</ref> Crystal twinning is common.
Solid solution exists between dolomite, the iron-dominant ankerite and the manganese-dominant 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. Lead, zinc, and cobalt also can substitute in the structure for magnesium. The mineral dolomite is closely related to 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 aquifers and contribute to karst terrain formation.<ref>Kaufmann, James. [https://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 anaerobic conditions in supersaturated saline lagoons such as those at the Rio de Janeiro coast of Brazil, namely, Lagoa Vermelha and Brejo do Espinho. There are many other localities where modern dolomite forms, notably along sabkhas 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|url-access=subscription}}</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|url-access=subscription}}</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 microbial metabolisms 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 extracellular polymeric substances (EPS) and microbial cell surfaces.<ref name=":1" /> This is likely the result from the complexation of both magnesium and calcium by carboxylic acids 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 the Cenozoic (Tertiary Era representing the last 66 million years of Earth's history) and 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 geochemical reaction has been coined "breaking Ostwald's step rule".<ref name="Deelman1999">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 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|url-access=subscription}}</ref> Dolomite is also found in continental saline lakes in Australia.<ref name="De_Deckker1988">{{cite journal | last1=De Deckker | first1=P. | last2=Last | first2=William M. | date=1988 | title=Modern dolomite deposition in continental, saline lakes, western Victoria, Australia | journal=Geology | volume=16 | issue=1 | issn=0091-7613 | doi=10.1130/0091-7613(1988)016<0029:MDDICS>2.3.CO;2 | page=29 | bibcode=1988Geo....16...29D | url=https://pubs.geoscienceworld.org/geology/article/16/1/29-32/204530 | access-date=2025-06-09| url-access=subscription }}</ref> The geochemical conditions considered to be favourable to the precipitation of dolomite in these lakes are their high salinity, high Mg/Ca ratios, and high alkalinity.<ref name="De_Deckker1988" /> However, dolomite can be volumetrically important in some Neogene platforms never subjected to elevated temperatures. Under such conditions of diagenesis, the long-term activity of the subsurface biosphere could play a role in dolomitization,<!-- microbial activity requires sufficient space and water. So, microbial activity is expected to be very low in compact clay formations, or intact rock matrices, with a very low hydraulic conductivity, in which the transfer of nutrients and toxins to, or from, microbial cells is limited by diffusion --> since diagenetic fluids of contrasting composition are mixed as a response to long-term climate changes controlled by 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|bibcode=2021Sedim..68.1797P |s2cid=234012426|issn=1365-3091|url-access=subscription}}</ref>{{Clarify|date=June 2025}}.
A recent biotic synthetic experiment claims to have precipitated ordered dolomite when 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|url-access=subscription}}</ref> A still perplexing example of an organogenic origin is that of the reported formation of dolomite in the 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 magnesium oxide, as well as in the Pidgeon process for the production of magnesium. It is an important petroleum reservoir rock, and serves as the host rock for large strata-bound Mississippi Valley-Type (MVT) ore deposits of base metals such as lead, zinc, and copper. Where calcite limestone is uncommon or too costly, dolomite is sometimes used in its place as a flux for the smelting of iron and steel. Large quantities of processed dolomite are used in the production of float glass.
In horticulture, dolomite and dolomitic limestone are added to soils and soilless potting mixes as a pH buffer and as a magnesium source. Pastures can be limed with dolomitic lime to raise their pH and where there is a magnesium deficiency. Dolomitic lime has also been used in environmental restoration and soil regeneration by increasing pH in soils previously affected by mining.<ref>{{Cite journal |last1=Nkongolo |first1=K. K. |last2=Michael |first2=P. |last3=Theriault |first3=G. |last4=Narendrula |first4=R. |last5=Castilloux |first5=P. |last6=Kalubi |first6=K. N. |last7=Beckett |first7=P. |last8=Spiers |first8=G. |date=2016-03-10 |title=Assessing Biological Impacts of Land Reclamation in a Mining Region in Canada: Effects of Dolomitic Lime Applications on Forest Ecosystems and Microbial Phospholipid Fatty Acid Signatures |url=https://doi.org/10.1007/s11270-016-2803-5 |journal=Water, Air, & Soil Pollution |volume=227 |issue=4 |article-number=104 |doi=10.1007/s11270-016-2803-5 |bibcode=2016WASP..227..104N |issn=0049-6979|url-access=subscription }}</ref>
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 catalyst for destruction of tar in the gasification of 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 particle detectors 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 cosmic rays without adding to 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|Dolomitization}} * {{annotated link|Evaporite}} * {{annotated link|List of minerals}} * {{annotated link|Magnesian Limestone}} * {{annotated link|Main Dolomite}} {{Clear}}
==References== {{Reflist}}
==Further reading== * {{Cite web |last1=McVean |first1=Ada |year=2023 |title='Dolomite problem' that has puzzled scientists for centuries may have finally been solved |url=https://www.chemistryworld.com/news/dolomite-problem-that-has-puzzled-scientists-for-centuries-may-have-finally-been-solved/4018596.article |access-date=2025-06-09 |website=Chemistry World |language=en}} * {{cite journal | last1=Kim | first1=Joonsoo | last2=Kimura | first2=Yuki | last3=Puchala | first3=Brian | last4=Yamazaki | first4=Tomoya | last5=Becker | first5=Udo | last6=Sun | first6=Wenhao | date=2023-11-24 | title=Dissolution enables dolomite crystal growth near ambient conditions | journal=Science | volume=382 | issue=6673 | pages=915–920 | issn=0036-8075 | doi=10.1126/science.adi3690 | pmid=37995221 | bibcode=2023Sci...382..915K | url=https://www.science.org/doi/10.1126/science.adi3690 | access-date=2025-06-09| url-access=subscription }}
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Category:Sedimentary rocks Category:Calcium minerals Category:Magnesium minerals Category:Carbonate minerals Category:Dolomite group Category:Dolomite (rock) Category:Trigonal minerals Category:Minerals in space group 148 Category:Evaporite Category:Luminescent minerals Category:Industrial minerals