Transparency: Opaque
Luster: Dull
Crystal System: Hexagonal
Cleavage: Perfect in one direction
Fracture: Irregular
Hardness: 2-3 on the Mohs scale
Streak: White or light gray
Other Identifying Properties: Fire clay is highly refractory, which means it can withstand high temperatures without melting or decomposing. It is also plastic, meaning it can be molded into various shapes.