Mineral Information and Data:

Ammoniojarosite
NH4Fe3+3(SO4)2(OH)6 [CNMNC approved formula]

Named in 1927 as the ammonium analog of jarosite.

IMA status : Redefined IMA Approved; 1987 ()
CLASSIFICATION 
Dana
(8th edition) :
30.02.05.04  
  (30) Anhydrous Sulfates Containing Hydroxyl or Halogen
  (30.02) where (A B)2 XO4 Zq
  (30.02.05) Alunite Group (Jarosite Subgroup)
  
Nickel-Strunz
(10th edition) :
07.BC.10
  (07) Sulfates (selenates, tellurates, chromates, molybdates, wolframates)
  (07.B) Sulfates (selenates, etc.) with Additional Anions, without H2O
  (07.BC) With medium-sized and large cations
  
Crystal system: Trigonal System
Point group (H-M): 3m — ditrigonal-pyramidal
Unit cell: a = 7.32Å, c = 17.5Å
Crystal Habit: Irregular flattened nodules of microscopic tabular grains
  
Color: Yellow
Diaphaneity: Transparent
Luster: Dull, waxy to earthy
Hardness (Mohs): 3.5 - 4.5
Measured Density: 3.03 g/cm3
Streak: Light yellow
  
Geologic Setting: Formed in black lignitic shales containing pyrite (Utah, USA).
Mineral Association: Tschermigite, epsomite, jarosite (Utah, USA); gypsum (Buffalo, Wyoming, USA); aluminite, natrojarosite (Zlatá Baña district, Slovakia).
  

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