Aphthitalite is a potassium sulfate mineral with the chemical formula: (K,Na)3Na(SO4)2.

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.

This article about a specific sulfate mineral is a stub.