Aluminium Silicate
Al2SiO5
|
Chemical name
Aluminium Silicate |
|
Mineral name
Andalusite |
|
Chemical formula
Al2SiO5 |
|
Melting point [°C]
Varies by form |
|
Crystal system
orthorhombic |
|
Crystal Class
orthorhombic-dipyramidal (2/m 2/m 2/m) |
|
Space Group
Pnnm |
|
Unit cell
a [Å]:7.78 b [Å]:7.92 c [Å]:5.57 |
|
Molecular weight [g/mol]
162.05 |
|
Formula units
Z=4 |
|
Frequent crystal surfaces
{110}, {001} |
|
Twinning
rare on {101} |
|
Mohs hardness
6.5 - 7.5 |
|
Density [g/cm3]
3.13 - 3.16 |
|
Cleavage
perfect on {110} |
|
Fracture / Tenacity
brittle to subconchoidal |
|
Color
pink, violet, yellow, green, white, gray |
|
Streak
white |
|
Transparency
transparent to nearly opaque |
|
Luster
vitreous |
|
Optical character
biaxial (-) |
|
Refractive Index
nα=1.629-1.640; nβ=1.633-1.644; nΥ=1.638-1.650 |
|
Birefringence δ
0.009 - 0.010 |
|
Pleochroism δ
strongly trichroic |
