Ilchagh (Iljaq) Salt mine, Dandy to Mahneshan road, Zanjan Province, Iran
© Maziar Nazari
Formula:   (K,Na)3Na(SO4)2
System:  Trigonal
Colour:  Colourless (rare), ...
Hardness: 3
Name: From the Greek άφθητος ("aphthitos"), "unalterable", and άλας ("halas"), "salt", in allusion to its stability in air.

Occurs in two widely diversified environments, both as an incrustation in volcanic fumaroles and as a constituent of oceanic and lacustrine salt deposits.

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Type Occurrence of Aphthitalite

Type Locality: Mt Vesuvius, Somma-Vesuvius Complex, Naples Province, Campania, Italy
Year of Discovery:  1835
Geological Setting of type material: Volcanic fumaroles
Associated Minerals at type locality: Thenardite  ,  Sylvite  ,  Jarosite  ,  Hematite

Physical Properties of Aphthitalite

Lustre:  Vitreous, Resinous
Diaphaneity (Transparency):  Transparent, Translucent, Opaque
Colour:  Colourless (rare), white, grey, bluish, greenish, reddish; colourless in transmitted light
Hardness (Mohs):  3
Tenacity:  Brittle
Cleavage: Imperfect/Fair
On {1010} fair; on {0001} poor.
Fracture:  Irregular/Uneven, Conchoidal
Density (measured):  2.656 - 2.71 g/cm3
Density (calculated):  2.72 g/cm3

Chemical Properties of Aphthitalite

Formula:    (K,Na)3Na(SO4)2
Essential elements: K, Na, O, S
All elements listed in formula:    K, Na, O, S

Photo:

This sample of aphthitalite is displayed in the Smithsonian Museum of Natural History.
More Info > Mindat: Aphthitalite

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