Witransaf Company Limited

Topaz Gemstone

Chemical Formula	Al₂SiO₄(F,OH)₂
Crystal System	Orthorhombic
Hardness	8 on the Mohs scale
Density	3.49 - 3.57 g/cm³
Refractive Index	1.609 - 1.643
Birefringence	0.008 - 0.016
Cleavage	Perfect basal
Luster	Vitreous
Transparency	Transparent to translucent
Color	Varies (commonly blue, yellow, pink)
Streak	White
Fracture	Conchoidal
Specific Gravity	3.4 - 3.6
Pleochroism	Weak
Optical Character	Biaxial positive
Fluorescence	Blue, yellow, white (under UV light)
Heat Sensitivity	Generally not sensitive