Exceptions are ammoniojarosite and destinezite (nearly insoluble); gypsum (slightly soluble); and slavikite (slowly soluble with decomposition).
Ammoniojarosite is common as crusts and aggregates of yellow to red-brown crystals (rhombohedron and pinacoid, or pseudocubic rhombohedron) to about 0.2 mm (Figs.
The mineral shows good cleavage normal to plates, and is found associated with magnesian apjohnite and epsomite, and sometimes with slavikite, ammoniojarosite, tschermigite, levinsonite-(Y), or zugshunstite-(Ce).
It is fairly widespread, but very sparse, occurring mostly on rock surfaces with ammoniojarosite. The mineral was identified by its color, luster and habit, and confirmed by SEM/SRF.
A surprising feature of the mineral assemblage at Alum Cave Bluff is the absence of potassium or sodium in the salt minerals, and the presence of ammonium equivalents (ammoniojarosite, tschermigite, possibly slavikite?).