Mineral Information and Data:

Ahlfeldite
NiSeO3 • 2H2O [CNMNC approved formula]

Named for Federico Ahlfeld (1892-192), German-Bolivian geologist and mineralogist who studied Bolivian minerals.

IMA status : Valid species (Pre-IMA 1935) Grandfathered
CLASSIFICATION 
Dana
(8th edition) :
34.02.03.03  
  (34) Selenites - Tellurites - Sulfites
  (34.02) as A++ XO3 · x(H2O)
  (34.02.03) Chalcomenite Group (Monoclinic)
  
Nickel-Strunz
(10th edition) :
04.JH.10
  (04) Oxides and Hydroxides
  (04.J) Arsenites, Antimonites, Bismuthites, Sulfites,
  (04.JH) Selenites without additional anions, with H2O
  
Crystal system: Monoclinic System
Point group (H-M): 2/m — prismatic
Unit cell: a = 7.53 Å, b = 8.76 Å, c = 6.43 Å, b = 99.083°
Crystal Habit: Crystals minute, elongated; crystalline crusts
  
Color: Pale green, apple-green, olive-green; brown, brownish pink, becoming pink with increasing cobalt content.
Diaphaneity: Transparent
Luster: Vitreous
Hardness (Mohs): 2 - 2.5
Measured Density: 3.37 g/cm3
Cleavage: 2; (110) and (103) fair
Streak: Light green
  
Polymorphism and Series: Forms a series with cobaltomenite.
Geologic Setting: A rare alteration product of nickel-bearing selenides and sulfides.
Mineral Association: Penroseite, chalcomenite, olsacherite, cerussite, anglesite (Pacajake mine, Bolivia); chalcomenite, olsacherite, lepidocrocite, goethite (El Drag´on mine, Bolivia)
  

 

Ahlfeldite
Green crusty ahlfeldite with massive dark gray krutaite
Origin: El Dragon, Colquechaca, Bolivia
Sample size: 2.5 x 2 x 1 cm
Photo: Tom Loomis

 

Ahlfeldite
(zoom-in of above)

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