Al2SiO5Orthorhombic
Sillimanite
Al2SiO5
SilicatesChemical FormulaAl2SiO5
Crystal SystemOrthorhombic
Mohs Hardness7.5
Specific Gravity3.24
ColorWhite, brown, green, gray
LusterVitreous to silky
StreakWhite
CleavageOne direction
FractureSplintery
Occurrence
Found in high-grade metamorphic rocks. Polymorph of andalusite and kyanite.