Schorl Tourmaline

Color: Black, usually opaque

Moh’s Hardness: 7-7.5

Refractive Index: 1.616-1.652

Critical Angle: 38.23°

Specific Gravity: 3.02-3.26

Cleavage: None

Fracture: Uneven, small conchoidal.

Dispersion: Medium (.017)

Heat Sensitivity: Not usually a problem

Dichroic: Opaque

Birefringence (double refraction): Medium (.014-.024)

Crystal structure: Hexagonal

Treatments: Generally there is no treatments with this kind of rough, it is opaque black.