Gold to green to brown. Alexandrite is a rare variety that changes color from green in daylight to red under incandescent light.

Physical Properties:

Chemistry: BeAl2O4
SG: 3.70-3.72
Cleavage: Imperfect in two directions
Fracture: None
Thermal sensitivity: None

Optical Properties:

RI: 1.744-1.755
Dispersion: 0.015 (medium)
Birefringence: 0.011 (medium)
Pleochroism: Weak (strong in Alexandrite)
Critical angle: 35°

Faceting angles (pavilion/crown):

Vargas: 42°/40°
Olson: 39°/37°
Soukup: 42°/37°
Roth: 42°/37°
MDR: 42°/37°
Schlagel: 40°/36°
Hashnu: 42°/39°
Sinkankas: 40°/40°
GIA: 42°/37°
GIA: 42°/37°
Cornwall: 40°/34°
Weikoff: 42°/38°
Carroll: 42.1°/35.3°

Cutting lap:

All grit sizes


Vargas: Diamond 100k on ceramic (low speed), aluminum oxide on tin/lead
Olson: Diamond 14k on tin
Soukup: Aluminum oxide on tin/lead, copper
Christiansen: Aluminum oxide on tin/lead, diamond 50k, 100k on tin, tin/lead, copper
Herbst: Diamond or aluminum oxide on metal or composite disc
Perkins: Diamond on BATT

Cabochon polishing:

Christiansen: Diamond 50k, 100k on wood or hard leather


According to shape. Alexandrite must be oriented by color.


Can be irradiated to enhance color. Sometimes alexandrite is oil-treated. Alexandrite is synthesized. A synthetic corundum with a color change from bluish-green to purple is often incorrectly called alexandrite.


Polishing with aluminum oxide is slow but gives good results. With diamond on a softer disc (metal), you can increase the speed.

Chrysoberyl rough

Chrysoberyl on Gemdat

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