Blödite

minerals

thenardite

mirabilite

carnallite

Formula: Na2Mg(SO4)2.4H2O
Hydrated normal sulphate, blödite group
Specific gravity: 2.23
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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