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Formula: K2Mg(SO4)2.4H2O
Hydrated normal sulphate, leonite group
Crystal System: Monoclinic
Specific gravity: 2.20 measured, 2.20 calculated
Hardness: 2½ to 3
Streak: White
Colour: Colourless, pale yellow; colourless in transmitted light
Solubility: Soluble in water, tastes slightly bitter
Environments
Marine salt deposits
Metamorphic environments
Fumeroles
Leonite is an uncommon secondary mineral of metamorphic
origin in marine salt deposits; it may also occur in volcanic fumaroles
(HOM).
Leonite may occur as a dehydration product of picromerite, and
leonite in turn dehydrates at 137oC to 147oC to
langbeinite and
arcanite
(Mindat).
The stability of leonite below 147oC shows that this mineral is limited to low-temperature
assemblages of hydrous sulphates and is expected mostly as an evaporite product on the surfaces of the Earth and
other water-saturated planets
(EJM 28.1.33-42).
Localities
At the type locality, the Douglashall III potash mine, Westeregeln, Börde-Hakel, Staßfurt potash deposit,
Saxony-Anhalt, Germany, leonite occurs in the rock salt deposit associated with
kainite and
halite
(Mindat).
At the Carlsbad Potash Mining District, Eddy County, New Mexico, USA, leonite is associated minerals with
kainite, polyhalite,
halite and sylvite
(HOM).
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