Specific gravity: 1.490
Hardness: 1½ to 2
Colour: Colourless, white
Solubility: Soluble in water
Mirabilite occurs in salt lakes, playas and springs, and as an efflorescence on alkali soils. At Great Salt Lake,
Utah, USA, it crystallises during winter due to decreased solubility at low temperatures
(Dana). It quickly dehydrates to thénardite in dry air
At Boron, Kramer district, Kern county, California, USA, thénardite pseudomorphs after mirabilite form as dehydration products (KL p187).
Mirabilite is unstable in dry air, when it loses its water and alters to thénardite, either as pseudomorphs after mirabilite, or just crumbled to a loose powder (MN).
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