| Langbeinite | |
|---|---|
 | |
| General | |
| Category | Sulfate mineral |
| Formula | K2Mg2(SO4)3 |
| IMA symbol | Lbn[1] |
| Strunz classification | 7.AC.10 |
| Crystal system | Cubic |
| Crystal class | Tetartoidal (23) (sameH-M symbol) |
| Space group | P213 |
| Unit cell | a = 9.92 Å; Z = 4 |
| Identification | |
| Color | Colorless with pale shades of yellow, pink, red, green, gray |
| 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 |
| Refractive index | n = 1.5329–1.5347 |
| Solubility | 280 g/L (20°C);[2] Slowly dissolves in water[3] |
| Other characteristics | Piezoelectric |
| References | [4][5][6] |
Langbeinite is apotassiummagnesiumsulfatemineral with the chemical formula K2Mg2(SO4)3. Langbeinite crystallizes in theisometric-tetartoidal (cubic) system as transparent colorless or white with pale tints of yellow to green and violet crystalline masses. It has a vitreousluster. TheMohs hardness is 3.5 to 4 and thespecific gravity is 2.83. The crystals arepiezoelectric.[4]
The mineral is anore of potassium and occurs in marineevaporite deposits in association withcarnallite,halite, andsylvite.[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 thelangbeinites, a family of substances with the same cubic structure, a tetrahedral anion, and large and small cations.
Related substances include hydrated saltsleonite (K2Mg(SO4)2·4H2O) andpicromerite (K2Mg(SO4)2·6H2O).
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