Color: Colorless, yellow, brown, red, blue, green, black.
Moh’s hardness: 10
Refractive index: 2.417-2.419
Critical angle: 24.5°
Specific gravity: 3.47-3.55
Fracture: Conchoidal, splintery
Dispersion: Strong (.044)
Heat sensitivity: None
Birefringence (double refraction): None
Crystal structure: Isometric
Treatments: Irradiation for enhancing colors. Fracture filling.
Cutting: Cutting can only be done with diamond on a cast iron lap. The amount of heat generated during cutting precludes the use of dop wax. A special mechanical device must be used to attach the diamond to the cutting machine.
Polishing: Diamond on cast iron lap.
Comments: Rough is difficult to obtain.