Starlite (Zircon)

Color: Blue

Moh’s hardness: 6.5-7.5

Type - Normal (high RI): Sometimes called high Zircon1.94-1.987 normal (higher refractive index) zircon is usually found in crystal form.

Critical Angle: 30.33°

Type - Metamict (lower RI): sometimes called low Zircon: 1.777-1.79 Metamict (lower refractive index) Zircon is usually found as river-worn pebbles

Critical Angle: 34.40°

Specific Gravity: 3.9-4.71

Cleavage: Imperfect 2 directions.

Fracture: Conchoidal, very brittle.

Dispersion: Strong (.038)

Heat Sensitivity: Yes, in my experience

Dichroic: Moderate to weak depending on color

Birefringence (double refraction): Strong (.06)

Crystal structure: Tetragonal

Treatments: Almost always heated