Gadolinium gallium garnet -GGG (gadolinium gallium oxide)
Color: Colorless, yellow, green, blue, pink, purple, red and orange.
Moh’s hardness: 7
Refractive index: 1.97
Critical angle: 30.5°
Specific gravity: 7.02
Dispersion: Strong (.045)
Heat sensitivity: Low
Birefringence (double refraction): None
Crystal structure: Isometric
Treatments: Synthetic material.
Cutting: Cuts and polishes like garnet.
Polishing: Polishes easily on tin or tin alloy laps with alumina, or diamond.