Mystic Topaz

Mineral group: Silicate
Chemistry: Al2[SiO4](F,OH) 2
Color: Rainbow colors
Crystal system: Orthorhombic
Fracture: Conchoidal, uneven
Mohs Scale hardness: 8
Refractive index: 1,610-1,638
Dispersion: 0,014
Birefringence: +0,008- 0,010
Pleochroism Present: Weak in thick sections
Streak: White
Specific gravity: 3,53- 3,56

Other:
This form of topas is colorless/white topaz with a layer of other material harden in high temperature, so called diffusion treatment. This gives the stone its wounderful spectrum of colors.