Amethyst (Quartz)

Color: Purple, violet to red-violet, blue/purple

Moh’s Hardness: 7

Refractive Index: 1.544-1.553

Critical Angle: 40.49°

Specific Gravity: 2.63-2.65

Cleavage: None

Fracture: Conchoidal

Dispersion: Medium (.013)

Heat Sensitivity: Can be... but is usually not a problem

Dichroism: very weak

Birefringence (double refraction): Weak (.009)

Crystal structure: Hexagonal

Treatments: Generally none.