Mineral Information and Data:

Arsenocrandallite
CaAl3(AsO4)(AsO3OH)(OH)6 [CNMNC approved formula]

Named for the "arsenic" in the composition, and relation to "crandallite.".

IMA status : Approved Species 1981 (IMA1980-060)
CLASSIFICATION 
Dana
(8th edition) :
42.07.04.01  
  (42) Hydrated Phosphates Containing Hydroxyl or Halogen
  (42.07) where (AB)5 (XO4)3 Zq · x(H2O)
  (42.07.04) Arsenocrandallite Group
  
Nickel-Strunz
(10th edition) :
08.BL.10
  (08) Phosphates, Arsenates, Vanadates
  (08.B) Phosphates, etc. with Additional Anions, without H2O
  (08.BL) With medium-sized and large cations, (OH, etc.):RO4 = 3:1
  
Crystal system: Trigonal System
Point group (H-M): 3m — ditrigonal-pyramidal
Unit cell: a = 7.08Å, c = 17.27Å
Crystal Habit: As spherulitic aggregates, to 0.1 mm, in reniform crusts.
  
Color: Blue-green to green
Diaphaneity: Semi-transparent
Luster: Vitreous
Hardness (Mohs): 5.5
Measured Density: 3.25 g/cm3
Fracture: Conchoidal
Streak: White
  
Geologic Setting: A secondary mineral on specimens from a mine dump (Neubulach, Germany).
Mineral Association: Brochantite, chalcophyllite, parnauite, barian pharmacosiderite, bulachite, arseniosiderite, mansfieldite, tetrahedrite–tennantite, azurite, malachite, barite, goethite, quartz (Neubulach, Germany); arsenogoyazite, beudantite, olivenite (Centennial Eureka mine, Utah, USA)
  

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