Aphthitalite
(repeating unit)(K,Na)3Na(SO4)2 IMA symbol Att[1] Strunz classification 7.AC.35 Crystal system Trigonal Crystal class Hexagonal scalenohedral (3m)
H-M symbol: (3 2/m) Space group P3m1 (no. 164) Unit cell a = 5.67, c = 7.33 [Å]; Z = 1 Identification Color White, colorless; gray, blue, green due to inclusions and impurities Crystal habit Tabular crystals (with distorted pseudo-orthorhombic habit); as bladed aggregates and in crusts Twinning On {0001} or repeated on {1120} Cleavage Fair on {1010}, poor on {0001} Fracture Conchoidal to uneven Tenacity Brittle Mohs scale hardness 3 Luster Vitreous to resinous Diaphaneity Transparent to opaque Specific gravity 2.66–2.71 Optical properties Uniaxial (+) (anomalously biaxial) Refractive index nω = 1.487 - 1.491 nε = 1.492 - 1.499 Birefringence δ = 0.005 Solubility In water References [2][3][4] 
H-M symbol: (3 2/m)
Aphthitalite is a potassium sulfate mineral with the chemical formula: (K,Na)3Na(SO4)2.
It was first described in 1835 for an occurrence on Mount Vesuvius, Italy. The name is from the Greek άφθητος, "unalterable", and άλας, "salt", for its stability in air.[2] It occurs as fumarolic incrustations in volcanic environments, as small crystals and masses in evaporite deposits and in guano deposits.[3][4] It occurs associated with thenardite, jarosite, sylvite and hematite in fumaroles; with blödite, syngenite, mirabilite, picromerite, borax and halite in evaporites; and with syngenite, whitlockite, monetite, niter and gypsum in guano deposits.[4]
References
Wikimedia Commons has media related to Aphthitalite.
- ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
- ^ a b Mindat.org
- ^ a b Webmineral data
- ^ a b c Handbook of Mineralogy
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