Sphene

Color: Brown, yellow, green, brownish-red

Moh’s Hardness: 5-5.5

Refractive Index: 1.995-2.05

Critical Angle: 30.17°

Specific Gravity: 3.52-3.54

Cleavage: Perfect

Fracture: conchoidal, brittle

Dispersion: Very strong (.051)

Heat Sensitivity: Moderate

Dichroic: Medium to strong

Birefringence (double refraction): Very strong (.105-.135)

Crystal Structure: Monoclinic

Treatments: Generally none