Physical characteristics

Physical characteristics loose sale price & Apple Green Peridot Gemstone Information

 

Properties of Alexandrite

Alexandrite (a variety of chrysoberyl)

 

  • Alexandrite Chemical composition: BeAl2O4 (small scale replacement of alumina by chromic oxide causes alexandrite's characteristic colors)
  • Class: oxides
  • Crystal system: orthorombic; 2/m2/m2/m
  • Crystal habit: prismatic crystals are elongated on c, and often tabular on {001}, with striations parallel to [100]
  • Twinning: commonly twinned on {130} resulting in a triangular or kite shaped form, repeated cyclic twinning produces pseudohexagonal "trillings"
  • Specific gravity: 3.68 - 3.75
  • Index of refraction: 1.745 - 1.759
  • Birefringence: weak (0.008-0.011)
  • Pleochroism: strong, X= red-purple, Y= orange, Z= green
  • Hardness: 8.5
  • Color: green in daylight and red-violet in incandescent light.
  • Luster: vitreous to greasy
  • Transparency: transparent
  • Cleavage: distinct on {011} perfect, indistinct on {010}, and poor on {100}
  • Fracture: conchoidal, brittle
  • Streak: white