Images
Formula: (NH4)2AlF3(SO4)
Halide
Crystal System: Orthorhombic
Specific gravity: 2.185 calculated
Streak: White
Colour: Colourless to white
Environments
Localities
At the type locality, the La Fossa crater, Vulcano Island, Lipari, Eolie Islands, Messina Province, Sicily, Italy,
thermessaite-(NH4) is found as a medium to high temperature (~250–300°C) fumarole encrustation at the rim
of the crater. It deposited as aggregates of minute (<0.2 mm) sharp prismatic crystals on the surface of a
pyroclastic breccia in association with
thermessaite, görgeyite,
sulphur, arcanite,
mascagnite and intermediate members of the
arcanite–mascagnite series
(MM 85.5.665-672, Mindat).
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