Mineral Information and Data:

Aspidolite
NaMg3(Si3Al)O10(OH)2 [CNMNC approved formula]

Named from the Greek "aspisidos", like a shield, alluding to the appearance of its crystals. Aspidolite is the Na analog of phlogopite.

IMA status : Redefined IMA Approved; 2006 (IMA2004-049)
CLASSIFICATION 
Dana
(8th edition) :
71.02.02b.13  
  (71) Phyllosilicate Sheets of Six-Membered Rings
  (71.02) with 2:1 Layers
  (71.02.02b) Mica Group (Biotite subgroup)
  
Nickel-Strunz
(10th edition) :
09.EC.20
  (09) Silicates
  (09.E) Phyllosilicates
  (09.EC) Phyllosilicates with mica sheets, composed of tetrahedral and octahedral nets
  
Crystal system: Monoclinic System
Point group (H-M): 2/m — prismatic
Unit cell: a = 5.291Å, b = 9.16Å, c = 10.12Å β = 105.1°
Crystal Habit: Occurs as light brown crystals interleaved with and rimmed by phlogopite plates from 0.1 to 1.2 mm long
  
Color: Light brown, white, greenish red
Hardness (Mohs): 2 -3
Cleavage: 1; (001) perfect
Streak: White
  
  
Comments: IMA2004-049 Natriumphlogopite - Renamed to Aspidolite -

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