Topase rarely occur in strong colours. By radiation and heating their colour can be changed. They are relatively hard, but easily fissile. Due to this great cleavage, extreme caution is required when grinding and grasping.

TOPAZ
Colour: colourless, yellow, red brown, light blue, red, violet, light green.
Mohs hardness: 8
Density: 3.49-3.57
Transparency: transparent
Fracture: muscular, uneven.