Mineral Information and Data:

Alumino-ferrotschermakite
[]Ca2[Fe2+3Al2](Si6Al2)O22(OH)2 [CNMNC approved formula]

Named for its composition and for Gustav Tschermak von Sessenegg (1836-1927), Austrian mineralogist.

IMA status : Approved Species 1997 ()
CLASSIFICATION 
Dana
(8th edition) :
66.01.03a.06a  (This Dana# Added)
  (66) Inosilicate Double-Width Unbranched Chains, W=2
  (66.01) with P=2 amphibole configuration
  (66.01.03a) Group 2, the calcic amphiboles
  
Nickel-Strunz
(10th edition) :
09.DE.10
  (09) Silicates
  (09.D) Inosilicates* Structural terminology per Liebau (1985)
  (09.DE) with 2-periodic double chains, Si4O11; Clinoamphiboles
  
Crystal system: Monoclinic System
Point group (H-M): 2/m — prismatic
Unit cell: a = 9.76 Å, b = 17.99 Å, c = 5.33 Å, b = 105.10°
Crystal Habit: prismatic crystals, as reaction rims on other minerals
Twinning: Simple or multiple parallel {100}
  
Color: Green
Diaphaneity: Transparent to translucent
Luster: Vitreous
Hardness (Mohs): 5 - 6
Measured Density: About 3.15 g/cm3
Cleavage: 3; {110} perfect, {100} and {001} parting
Tenacity: Brittle
Streak: White
  
Geologic Setting: Formed in eclogites and other ultramafic igneous rocks, and in medium- to high-grade metamorphic rocks, typically amphibolites.
  
Synonyms/varieties: Ferro-aluminotschermakite

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