Color: Pink, violet, cornflower-blue
Moh’s Hardness: 6-7
Refractive Index: 1.655-1.68
Critical Angle: 37.31°
Specific Gravity: 3.16-3.20
Cleavage: perfect in 2 directions
Fracture: Uneven, very splintery
Heat Sensitivity: Yes
Birefringence (double refraction): Medium (.015)
Crystal Structure: Monoclinic
What I prefer to polishing with: Tin lap with Alumina oxide. Zinc laps with 8,000 pre-polish and 50,000 polish.
Jeff’s Comments: Saw as little as possible, it is very tender and will fall apart from too much sawing and the vibration. Orient for best color which is usually the “c”, cut slightly off the from the cleavage plane (“c”). Use a fine lap during the cutting process, a coarse lap tends to aggravate cleavage problems and chipping.