Mineral Information and Data:

Apjohnite
Mn2+Al2(SO4)4 • 22H2O [CNMNC approved formula]

Named for James Apjohn (1796-1886), Professor of Chemistry and Mineralogy, Trinity College, Dublin, Ireland.

IMA status : Valid species (Pre-IMA 1838) Grandfathered
CLASSIFICATION 
Dana
(8th edition) :
29.07.03.03  
  (29) Hydrated Acid and Sulfates
  (29.07) where A (B)2 (XO4)4 · x(H2O)
  (29.07.03) Halotrichite Group (Monoclinic with 22 H2O)
  
Nickel-Strunz
(10th edition) :
07.CB.85
  (07) Sulfates (selenates, tellurates, chromates, molybdates, wolframates)
  (07.C) Sulfates (selenates, etc.) without Additional Anions, with H2O
  (07.CB) With only medium-sized cations
  
Crystal system: Monoclinic System
Point group (H-M): 2/m — prismatic
Unit cell: a = 6.198 Å, b = 24.347 Å, c = 21.266 Å, b = 100.28°
Crystal Habit: Masses, crusts of fibrous or acicular crystals
  
Color: Colorless, white, pale shades of yellow, green, pink
Diaphaneity: Transparent
Luster: Silky
Hardness (Mohs): 1.5
Measured Density: 1.81 g/cm3
Streak: White
  
Geologic Setting: As efflorescences.
Mineral Association: Halotrichite, pickeringite, gunningite, copiapite, epsomite
  
Other Properties: H2O Soluble.

 

Apjohnite
Origin: Pintados, Iquique, Chile
Sample size: 1.5 x 2 cm
Photo: Diederik Visser

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