Wulfenite (lead molybdate)
Color: orange, red, yellow and colorless.
Moh’s hardness: 2.5-3
Refractive index: 2.3
Critical angle: 25.5°
Specific gravity: 7
Cleavage: Distinct in one direction.
Fracture: Uneven, very brittle.
Heat sensitivity: Extremely high.
Birefringence (double refraction): Very strong (.122)
Crystal structure: Tetragonal.
Cutting: The brittle nature of wulfenite makes it very difficult to cut. Use an extra fine lap and protect the stone from any kind of shock. Adhesives are essential for dopping.
Polishing: Alumina or tin oxide on wax lap. The trailing end of the facet tends to round over.