Langbeinite

Langbeinite is a potassium magnesium sulfate mineral with 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 has a vitreous luster. The Mohs hardness is 3.5 to 4 and the specific gravity is 2.83. The crystals are phosphorescent and piezoelectric.
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Noun
1. a mineral consisting of potassium magnesium double sulphate; used as a fertilizer
(hypernym) mineral
(substance-meronym) potassium, K, atomic number 19

General Information:
 Chemical Formula:
K2Mg2(SO4)3
 Composition:
(Molecular Weight = 415.00 gm)
Potassium 18.84 % K 
Magnesium 11.71 % Mg
Sulfur 23.18 % S 
Oxygen 46.26 % O 
 Empirical Formula:
K2Mg2(SO4)3
 Environment:
Marine evaporite deposits.
Physical Properties:
 Cleavage:
None
 Color:
colorless, violet, greenish, gray, or yellowish.
 Density:
2.83
 Diaphaniety:
Transparent to Translucent
 Hardness:
3.5-4 - Copper Penny-Flourite
 Luminescence:
Phosphorescent.
 Luster:
Vitreous (Glassy)
 Streak:
white
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