Ammoniojarosite
Ammoniojarosite is an IMA-recognized mineral species in the sulfate class, with the chemical formula (NH₄)Fe³⁺₃(SO₄)₂(OH)₆.
It crystallizes in the hexagonal crystal system (space group R-3m). It is a member of the Alunite-Alunite structural group.
Key properties: specific gravity 3.112; Dull, may be waxy to earthy luster; optically uniaxial.
IMA symbol Ajrs, IMA status: approved, named in 1927.
Formed in black lignitic shales containing pyrite (Utah, USA).
It is found associated with Tschermigite, epsomite, jarosite (Utah, USA); gypsum (Buffalo, Wyoming, USA); aluminite, natrojarosite (Zlatá Baňa district, Slovakia).
As the ammonium analog of jarosite.
Index entry. This entry combines official IMA/RRUFF species data with published physical-property data — a full written entry hasn’t been published yet.
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