Formula: Na2Mg(SO4)2.4H2O
Hydrated normal sulphate, blödite group
Crystal System: Monoclinic
Specific gravity: 2.218 to 2.24 measured, 2.23 calculated
Hardness: 2½ to 3
Colour: Colourless, bluish-green, reddish; colourless in transmitted light.
Solubility: Readily soluble in cold water
Environments
Evaporite deposits
Metamorphic environments
Volcanic sublimates
Blödite occurs in lacustrine salt deposits and salt efflorescences, probably as a product of metamorphism of marine salt deposits,
in nitrate deposits, and it may be a volcanic sublimate. In marine salt deposits associated minerals include
halite, kainite,
carnallite and polyhalite. In lacustrine salt
deposits associated minerals include halite, thénardite
and mirabilite
(HOM).
Localities
At the type locality, Ischler Salzberg, Perneck, Bad Ischl, Gmunden District, Upper Austria, Austria, blödite occursin an oceanic
salt deposit
(Mindat).
Alteration
Dehydration, which is endothermic, occurs at 107oC and 227oC; the first product is
löweite; at the second step this transforms into
α-Na2Mg2(SO4)3 and vanthoffite or
thénardite
(Mindat).
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