langbeinite

{{Short description|Potassium magnesium sulfate mineral}}

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{{Infobox mineral

| name = Langbeinite

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| image = File:Langbeinite-553833.jpg

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| category = Sulfate mineral

| formula = K₂Mg₂(SO₄)₃

| IMAsymbol = Lbn{{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}}

| molweight =

| strunz = 7.AC.10

| dana =

| system = Cubic

| class = Tetartoidal (23)
(same H-M symbol)

| symmetry = P2₁3

| unit cell = a = 9.92 Å; Z = 4

| color = Colorless with pale shades of yellow, pink, red, green, gray

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| habit = As nodules, disseminated grains, bedded massive

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| fracture = Conchoidal

| tenacity = Brittle

| mohs = 3.5–4

| luster = Vitreous

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| diaphaneity = Transparent

| gravity = 2.83

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| opticalprop = Isotropic

| refractive = n = 1.5329–1.5347

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| solubility = 280 g/L (20°C);{{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 }} Slowly dissolves in water{{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}}

| impurities =

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| other = Piezoelectric

| references = [http://rruff.geo.arizona.edu/doclib/hom/langbeinite.pdf Handbook of Mineralogy][http://www.mindat.org/min-2320.html Mindat with location data][http://www.webmineral.com/data/Langbeinite.shtml Webmineral data]

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Langbeinite is a potassium magnesium sulfate mineral with the chemical formula K₂Mg₂(SO₄)₃. 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.

The mineral is an ore of potassium and occurs in marine evaporite deposits in association with carnallite, halite, and sylvite.

It was first described in 1891 for an occurrence in Wilhelmshall, Halberstadt, Saxony-Anhalt, Germany, and named for A. Langbein of Leopoldshall, Germany.

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 (K₂Mg(SO₄)₂·4H₂O) and picromerite (K₂Mg(SO₄)₂·6H₂O).