Cordierite
Mg2AI3(ALSi5O18)
Chemical name
Cordierite |
Chemical formula
Mg2AI3(ALSi5O18) |
Crystal system
orthorhombic |
Crystal Class
Dipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m) |
Space Group
Cccm |
Unit cell
a [Å]:17079 b [Å]:9730 c [Å]:9356 |
Formula units
Z = 4 |
Twinning
Common on {110}, {130}, simple, lamellar, cyclical |
Mohs hardness
7 - 7,5 |
Density [g/cm3]
2.6 - 2.66 |
Cleavage
Fair on {100}, poor on {001} and {010} |
Fracture / Tenacity
Subconchoidal, brittle |
Color
Blue, smoky blue, bluish violet; greenish, yellowish brown, gray; colorless to very pale blue in thin section in transmitted light |
Streak
White |
Transparency
Transparent to translucent |
Luster
Greasy or vitreous |
Refractive Index
nα = 1.527 - 1.560 nβ = 1.532 - 1.574 nΥ = 1.538 - 1.578 Indices increase with Fe content. |
Pleochroism δ
X = pale yellow, green; Y = violet, blue-violet; Z = pale blue |