Dark brown perfect crystals of the extremely rare new mineral theresiaite (IMA 2013-050) from the famous locality La Fossa Crater (Vulcano Island, Aeolian Islands, Sicily, Italy), on adranosite crystals. Formula: (NH4)3KNa2Fe2+Fe3+(SO4)3Cl5. The sample is completely sealed in nitrogen atmosphere, so it is perfectly stable. It is a one locality mineral worldwide, and in La Fossa Crater only a few specimens have been found, so it is a very sought after mineral!. The photo have been made through the plasticbox, so quality is not very high. — Photo: David Hospital · CC BY-SA 4.0
Adranosite
An ammonium-bearing sulfate-chloride found in the La Fossa crater on Vulcano in Italy's Aeolian Islands.
Intro adapted from Wikipedia (CC BY-SA).
Adranosite is an IMA-recognized mineral species in the sulfate class, with the chemical formula (NH₄)₄NaAl₂(SO₄)₄Cl(OH)₂.
It crystallizes in the tetragonal crystal system (space group I4_1/acd). It is a member of the Adranosite structural group.
Key properties: specific gravity 2.15; White streak; Vitreous luster; optically uniaxial.
IMA symbol Arn, IMA status: approved, named in 2008.
A sublimate on pyroclastic breccia around an active volcanic fumarole.
It is found associated with Aiolosite, alunite, anhydrite, bismuthinite, sassolite, dimicheleite-(Br), dimicheleite-(Cl), demicheleite-(I).
The name refers to the ancient god of fire, Adranos.