Anhydrous normal sulphate
Specific gravity: 2.66 to 2.71
Colour: Colourless (rare), white, grey, bluish, greenish, reddish; colourless in transmitted light
Solubility: Soluble in water and in acids
Aphthitalite occurs in two different environments. It is formed in volcanoes as uncommon incrustations in
it may deposit from volcanic gas during cooling from about 800oC down to 400oC,
together with thénardite.
It also occurs in marine and continental evaporite deposits
(Dana, Webmin, Mindat, HOM). A third occurrence is in guano deposits, which are typically ammonian
In fumeroles it is associated with thénardite, jarosite, sylvite and hematite. In evaporites it is associated with blödite, syngenite, mirabilite, picromerite, borax and halite. In guano deposits it is associated with syngenite, whitlockite, monetite, niter and gypsum (HOM).
At the type locality, Mount Vesuvius, Somma-Vesuvius Complex, Naples, Campania, Italy, aphthitalite occurs in volcanic fumaroles associated with thénardite, sylvite, jarosite and hematite (Mindat).
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