Crystal System: Trigonal
Status of Occurrence: Unconfirmed Occurrence
Distribution: Rare
Chemical Composition: Ammonium iron sulphate hydroxide
Chemical Formula: NH4(Fe3+)3(SO4)2(OH)6
Method(s) of Verification: XRD at the National Museum of Wales (XRD no. NMW X-1775). Some form of chemical analysis is desirable before definitive identification is made.

Chemical Group:

  • Sulphates

Geological Context:

  • Supergene: post-mining oxidation & weathering deposits
Introduction: a secondary iron sulphate mineral formed by the decay of pyrite, particularly in dark shales.
Occurrence in Wales: ammoniojarosite has tentatively been identified intimately associated with copiapite and gypsum in ocherous yellow crusts on a sample (National Museum of Wales collection, no. NMW 85.14G.M.64) picked up from the dumps of an old iron mine near Taff's Well in South Wales.

Key Localities:

There are no key localities for this specimen.


There are no references for this specimen.