Color: Pale yellow to gray with play of color, quality material has a rainbow like sheen

Moh’s Hardness: 6-6.5

Refractive Index: 1.52-1.568

Critical Angle: 41.14°

Specific Gravity: 2.69-2.70

Cleavage: Perfect

Fracture: Uneven, somewhat brittle.

Dispersion: Low (.012), but the combination of a high polish and minute inclusions can simulate the effect of moderate dispersion.

Heat Sensitivity: Moderate in my experience

Dichroism: Weak

Birefringence (double refraction): Weak to medium (.005-.01)

Crystal Structure: Triclinic

Treatments: Generally none