Langbeinite: Properties and Occurrences

Langbeinite is a potassium magnesium sulfate mineral with the chemical formula K2Mg2(SO4)3. Langbeinite crystallizes in the isometric-tetartoidal system as transparent colorless or white with pale tints of yellow to green and violet crystalline masses. It is a unique source of plant nutrition since three essential nutrients combine naturally into one mineral. It is a mineral that is a sulfate of potassium and magnesium used in the fertilizer industry

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

General Information

  • Category: Sulfate mineral
  • Formula: (repeating unit) K2Mg2(SO4)3.
  • Crystal system: Cubic
  • Crystal class: Tetartoidal (23) (same H-M symbol)
  • Color: Colorless with pale shades of yellow, pink, red, green, gray.

Fig: Langbeinite

Properties

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.

  • Crystal habit: As nodules, disseminated grains, bedded massive
  • Fracture: Conchoidal
  • Tenacity: Brittle
  • Mohs scale hardness: 3.5 – 4
  • Luster: Vitreous
  • Diaphaneity: Transparent
  • Specific gravity: 2.83
  • Optical properties: Isotropic.

Occurrences

Langbeinite gives its name to the langbeinites, a family of substances with the same cubic structure, a tetrahedral anion, and large and small cations. It is a mineral that is often found in salt deposits as a natural sulfate of potassium and magnesium, used as a source of potash

Related substances include hydrated salts leonite (K2Mg(SO4)2·4H2O) and picromerite (K2Mg(SO4)2·6H2O).

 

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