Langbeinite
General
CategorySulfate mineral
Formula
(repeating unit)
K2Mg2(SO4)3
IMA symbolLbn[1]
Strunz classification7.AC.10
Crystal systemCubic
Crystal classTetartoidal (23)
(same H-M symbol)
Space groupP213
Unit cella = 9.92 Å; Z = 4
Identification
ColorColorless with pale shades of yellow, pink, red, green, gray
Crystal habitAs nodules, disseminated grains, bedded massive
FractureConchoidal
TenacityBrittle
Mohs scale hardness3.5–4
LusterVitreous
DiaphaneityTransparent
Specific gravity2.83
Optical propertiesIsotropic
Refractive indexn = 1.5329–1.5347
Solubility280 g/L (20°C);[2] Slowly dissolves in water[3]
Other characteristicsPiezoelectric
References[4][5][6]

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.[4]

The mineral is an ore of potassium and occurs in marine evaporite deposits in association with carnallite, halite, and sylvite.[4]

It was first described in 1891 for an occurrence in Wilhelmshall, Halberstadt, Saxony-Anhalt, Germany, and named for A. Langbein of Leopoldshall, Germany.[4][5]

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).

References

  1. Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. Artiola, Janick F.; Gebrekidan, Heluf; Carty, David J. (October 2000). "Use of langbeinite to reclaim sodic and saline sodic soils". Communications in Soil Science and Plant Analysis. 31 (17–18): 2829–2842. doi:10.1080/00103620009370631. S2CID 95055306.
  3. Harley, G. T.; Atwood, G. E. (January 1947). "Langbeinite... Mining and processing". Industrial & Engineering Chemistry. 39 (1): 43–47. doi:10.1021/ie50445a020.
  4. 1 2 3 4 Handbook of Mineralogy
  5. 1 2 Mindat with location data
  6. Webmineral data


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