Danburite

Color: Colorless, pink, wine-yellow and brownish.

Moh’s Hardness: 7

Refractive Index: 1.63-1.636

Critical Angle: 37.84°

Specific Gravity: 3.0

Cleavage: Imperfect

Fracture: Uneven, conchoidal

Dispersion: Medium (.017)

Heat Sensitivity: Yes in my experience

Birefringence (double refraction): Weak (.006)

Crystal Structure: Orthorhombic

Treatments: Generally none, sometimes can be irradiated.