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