Topaz
Chemical Formula	Al2SiO4(F,OH)2
Species	Silicates
Crystal System	Orthorhombic
Mohs Scale	8
Specific Gravity	3.4-3.6
Color	Colourless, white, pale blue, light green, yellow, yellowish brown, or red
Streak	White
Luster	Vitreous
Refractive Index	n = 1.606 - 1.629 n = 1.609 - 1.631 n = 1.616 - 1.638
Diaphaneity	Transparent, Translucent
Cleavage	Perfect
Fracture	Irregular/Uneven, Sub-Conchoidal
Crystal Habit：Prismatic crystals with faces striated parallel to long dimension; also columnar, compact, massive
Geological Setting：As a rock forming mineral in igneous rocks, pegmatites and rhyolites, hydrothermal veins, metamorphic rocks and greisens.