Mineral Information and Data:

Aluminite
Al2SO4(OH)4 • 7H2O [CNMNC approved formula]

Named after its chemical composition.

IMA status : Valid species (Pre-IMA 1807) Grandfathered
CLASSIFICATION 
Dana
(8th edition) :
31.07.04.01  
  (31) Hydrated Sulfates Containing Hydroxyl or Halogen
  (31.07) where (A+ B++)2 (XO4) Zq · x(H2O)
  (31.07.04)
  
Nickel-Strunz
(10th edition) :
07.DC.05
  (07) Sulfates (selenates, tellurates, chromates, molybdates, wolframates)
  (07.D) Sulfates (selenates, etc.) with additional anions, with H2O
  (07.DC) With only medium-sized cations; chains of edge-sharing octahedra
  
Crystal system: Monoclinic System
Point group (H-M): 2/m — prismatic
Unit cell: a = 7.44 Å, b = 15.583 Å, c = 11.7 Å, b = 110.18°
Crystal Habit: Nodular masses of minute fibres; spherulitic; veinlets
  
Color: White to grayish
Diaphaneity: Translucent, opaque if massive.
Luster: Dull, earthy
Hardness (Mohs): 1 - 2
Measured Density: 1.66 - 1.82 g/cm3
Tenacity: Friable
Fracture: Earthy, in aggregates.
Streak: White
  
Geologic Setting: Typically in clays or lignites, formed by the reaction of sulfate-bearing solutions from the decomposition of marcasite or pyrite at moderate temperatures with aluminous silicates; as a volcanic sublimate; in sulfur deposits; rarely in caves.
Mineral Association: Basaluminite, gibbsite, epsomite, gypsum, celestine, dolomite, goethite
  

 

Aluminite
White nodule of aluminite
Origin: Halle, Saxony-Anhalt, Germany (type locality)
Sample size: 4 cm diameter
Photo and Owner: Thomas Witzke

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