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Formula: K2AlF3(SO4)
Sulphate
Crystal System: Orthorhombic
Specific gravity: 2.77 measured, 2.790 calculated
Streak: White
Colour: Colourless to white
Luminescence: No fluorescence under long wave or short wave UV
Environments
Localities
At the type locality, La Fossa crater, Vulcano Island, Lipari, Eolie Islands, Metropolitan City of Messina, Sicily, Italy,
thermessaite is found in active medium- to high-temperature fumaroles (300 to 350°C) at the rim of the crater. It
occurs as sharp translucent crystals up to 0.25 mm in size in an altered pyroclastic
breccia, together with alunite,
sassolite, anhydrite and
metavoltine
(CM 46.693-700).
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