Mineral - Cordierite
Cordierite
Chemical Properties
Mineral Class
Silicates
Toxicity
none
Formula
Mg₂Al₃[AlSi₅O₁₈][
Unit Cell
a=17.08 b=9.73 c=9.36 Z=4
Physical Properties
Hardness
7 - 7.5
Streak
white
Density
Normal (2-3,5)
Cleavage
Imperfect after {100}, indistinct after {001} and {010}
Fracture
conchoidal
Tenacity
Brittle
Optical Properties
Color
bluecolorless
Birefringence
0.018
Luster
Vitreous
Transparency
translucent,
transparent
Pleochroism
X = Gelb-Grün
Y = Blau-Violett
Z = Blau
Geomineralogical Properties
Crystal System
orthorhombic
Point Group
orthorhombic-dipyramidal - 2/m 2/m 2/m
Space Group
Cccm (66)
Habit
granular, prismatic
Formation
Metamorphism
Paragenesis
Twinning
Rarity
Common
Synonyms
Cordierite
Composition
Elements
Mass
SiO₂
50.20
TiO₂
0.01
Al₂O₃
33.50
Fe₂O₃
0.14
FeO
0.84
MnO
0.06
MgO
12.80
CaO
0.23
Na₂O
0.26
K₂O
0.14
H₂O
1.81
Australia (Dana 1892)
Groups and Members
Beryl-Supergroup
Cordierite-Group