Aphthitalite

sulphate

thenardite

Formula: K3Na(SO4)2 anhydrous normal sulphate
Specific gravity: 2.66 to 2.71
Hardness: 3
Streak: White
Colour: Colourless (rare), white, grey, bluish, greenish, reddish; colourless in transmitted light
Solubility: Soluble in water
Environments:

Sedimentary environments
Fumeroles

Aphthitalite occurs in two different environments. It is formed in volcanoes as incrustations in fumeroles, where it may deposit from volcanic gas during cooling from about 800 down to 400oC, together with thénardite. (Mindat) It also occurs in lacustrine (lake) salt deposits (Dana).

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