{{Short description|Potassium magnesium sulfate mineral}} {{Redirect|K-Mag|other uses|KMAG (disambiguation)}} {{Infobox mineral | name = Langbeinite | boxwidth = | boxbgcolor = | image = File:Langbeinite-553833.jpg | imagesize = 260px | alt = | caption = | category = Sulfate mineral | formula = K<sub>2</sub>Mg<sub>2</sub>(SO<sub>4</sub>)<sub>3</sub> | IMAsymbol = Lbn<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 = 7.AC.10 | dana = | system = Cubic | class = Tetartoidal (23) <br /><small>(same H-M symbol)</small> | symmetry = ''P2''<sub>1</sub>3 | unit cell = a = 9.92 Å; Z = 4 | color = Colorless with pale shades of yellow, pink, red, green, gray | colour = | habit = As nodules, disseminated grains, bedded massive | twinning = | cleavage = | fracture = Conchoidal | tenacity = Brittle | mohs = 3.5–4 | luster = Vitreous | streak = | diaphaneity = Transparent | gravity = 2.83 | density = | polish = | opticalprop = Isotropic | refractive = n = 1.5329–1.5347 | birefringence = | pleochroism = | 2V = | dispersion = | extinction = | length fast/slow = | fluorescence = | absorption = | melt = | fusibility = | diagnostic = | solubility = 280 g/L (20°C);<ref>{{cite journal |last1=Artiola |first1=Janick F. |last2=Gebrekidan |first2=Heluf |last3=Carty |first3=David J. |title=Use of langbeinite to reclaim sodic and saline sodic soils |journal=Communications in Soil Science and Plant Analysis |date=October 2000 |volume=31 |issue=17–18 |pages=2829–2842 |doi=10.1080/00103620009370631|bibcode=2000CSSPA..31.2829A |s2cid=95055306 }}</ref> Slowly dissolves in water<ref>{{cite journal |last1=Harley |first1=G. T. |last2=Atwood |first2=G. E. |title=Langbeinite... Mining and processing |journal=Industrial & Engineering Chemistry |date=January 1947 |volume=39 |issue=1 |pages=43–47 |doi=10.1021/ie50445a020}}</ref> | impurities = | alteration = | other = Piezoelectric | references = <ref name=HBM>[http://rruff.geo.arizona.edu/doclib/hom/langbeinite.pdf Handbook of Mineralogy]</ref><ref name=Mindat>[http://www.mindat.org/min-2320.html Mindat with location data]</ref><ref name=Webmin>[http://www.webmineral.com/data/Langbeinite.shtml Webmineral data]</ref> }}
'''Langbeinite''' is a potassium magnesium sulfate mineral with the chemical formula K<sub>2</sub>Mg<sub>2</sub>(SO<sub>4</sub>)<sub>3</sub>. Langbeinite crystallizes in the isometric-tetartoidal (cubic) system as transparent colorless or white with pale tints of yellow to green and violet crystalline masses. It has a vitreous luster. The Mohs hardness is 3.5 to 4 and the specific gravity is 2.83. The crystals are piezoelectric.<ref name=HBM/>
The mineral is an ore of potassium and occurs in marine evaporite deposits in association with carnallite, halite, and sylvite.<ref name=HBM/>
It was first described in 1891 for an occurrence in Wilhelmshall, Halberstadt, Saxony-Anhalt, Germany, and named for A. Langbein of Leopoldshall, Germany.<ref name=HBM/><ref name=Mindat/>
Langbeinite gives its name to the langbeinites, a family of substances with the same cubic structure, a tetrahedral anion, and large and small cations.
Related substances include hydrated salts leonite (K<sub>2</sub>Mg(SO<sub>4</sub>)<sub>2</sub>·4H<sub>2</sub>O) and picromerite (K<sub>2</sub>Mg(SO<sub>4</sub>)<sub>2</sub>·6H<sub>2</sub>O).
==References== {{Reflist}}
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Category:Potassium minerals Category:Magnesium minerals Category:Sulfate minerals Category:Evaporite Category:Cubic minerals Category:Minerals in space group 198 Category:Minerals described in 1891
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