Cat's Eye is of the Chrysoberyl group Which includes Alexandrite. Cat's Eye (Greek - Light Wave), is an attractive variety. Thin parallel inclusions create a silver-white line which appears as a white moving light ray in a carbon-cut stone. It's this effect that gives chrysoberyl cat's eye it's name. "Cat's eye" by itself always refers to chyrsoberyl, all other cats eye must be designated by an additional name. There are deposits in Sri Lanka, Brazil, and China.

Chyrsoberyl

• Color : Golden yellow, green-yellow, brown
• Color of streak : White
• Mohs' hardness : 8 1/2
• Specific gravity : 3.70-3.72
• Cleavage : Imperfect
• Fracture : Weak, conchoidal
• Crystal system : Orthorhombic; long brismatic crystals, intergrown triplets
• Chemical composition : Al2(BeO4) Beryllium aluminum oxide
• Transparency : Transparent
• Refractive index : 1.44-1.744
• Double refraction : +0.011
• Dispersion : 0.015
• Pleochroism : Very weak; reddish-yellow, yellow, light green, green
• Absorption spectrum : 5040, 4950, 4850, 4450
• Fluoresence : Usually none
  Green: weak; dark red