Color: Black, usually opaque
Moh’s Hardness: 7-7.5
Refractive Index: 1.616-1.652
Critical Angle: 38.23°
Specific Gravity: 3.02-3.26
Fracture: Uneven, small conchoidal.
Heat Sensitivity: Not usually a problem
Birefringence (double refraction): Medium (.014-.024)
Crystal structure: Hexagonal
Treatments: Generally there is no treatments with this kind of rough, it is opaque black.
What I prefer to polishing with: Alumina oxide with a tin lap (scored).
Jeff’s Comments: Cuts and polishes like any other Tourmaline, usually no problems… The material is black and generally not cut much, although I do know people that use Schorl for intarsia and inlay work because it is harder and will wear better that most other traditional materials (like jet or coral). Aslo is makes very nice cut beads.
Design Notes: About any design will work.