Mineral Information and Data:

Armbrusterite
Na6K5Mn3+Mn2+14[Si9O22]4(OH)10 • 4H2O [CNMNC approved formula]

Named for Thomas Armbruster (b. 1950; University of Berne) for his outstanding contribution to structural mineralogy and crystallography, especially to the study of Mn-rich minerals .

IMA status : Approved Species 2005 (IMA2005-035)
CLASSIFICATION 
Dana
(8th edition) :
74.01.03.02  
  (74) Phyllosilicate Modulated Layers
  (74.01) with joined islands
  (74.01.03)
  
Nickel-Strunz
(10th edition) :
09.EG.65
  (09) Silicates
  (09.E) Phyllosilicates
  (09.EG) Double nets with 6-membered and larger rings
  
Crystal system: Monoclinic System
Point group (H-M): 2/m — prismatic
Unit cell: a = 17.3335Å, b = 23.539Å, c = 13.4895Å β = 115.069°
Crystal Habit: Occurs as split, curved crystals and spherulites(~2mm diameter)
  
Color: Dark reddish-brown
Diaphaneity: Translucent
Luster: Vitreous
Hardness (Mohs): 3.5
Measured Density: 2.78 g/cm3
Cleavage: {001} Perfect
Tenacity: Brittle
Fracture: Uneven
Streak: Light-brown
  
  

 

Armbrusterite
Translucent yellow-brown crystals of armbrusterite on small fragment of brown matrix.
Origin: Kirovskii Mine, Mt. Kukisvumchorr, Khibiny, Kola Peninsula, Russia.
Sample size: 5x3x2 mm
Photo: © John Betts - Fine Minerals

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