Emerald (Beryl)

Color: Green

Moh’s Hardness: 7.5-8

Refractive Index: 1.57-1.60

Critical Angle: 39.87°

Specific Gravity: 2.65-2.75

Cleavage: None

Fracture: Conchoidal, tough

Dispersion: Medium (.014)

Heat Sensitivity: Yes, especially depending on treatments

Dichroism:Weak

Birefringence (double refraction): Weak (.006-.009)

Crystal Structure: Hexagonal

Treatments: Almost all Emeralds are treated to improve color and durability. Assume that any Emerald you see is treated.