Topaz Facet / Faceting Information
Color: Blue, colorless, pink, orange, red, champagne, sherry-brown, brown and yellow
Moh’s Hardness: 8
Refractive Index: 1.61-1.638
Critical Angle: 38°
Specific Gravity: 3.53-3.56
Cleavage: Very perfect in one direction
Fracture: Conchoidal, uneven
Heat Sensitivity: None
Dichroic: Weak to strong depending on color
Birefringence (double refraction): Weak (.008-.01)
Crystal Structure: Orthorhombic
Treatments: Blue is almost always irradiated and heated, some champagne and root beer colors are too.
What I prefer to polishing with: Alumina oxide on a Tin lap, Spectra Ultralap, 8,000 diamond pre-polish 50,000 diamond polish on a Zinc laps
Jeff’s Comments: Orient the rough at least 7 to 10 degrees away from the cleavage plane (“c” axis). The cleavage on topaz is perfect, and looks almost like a polished surface. Commercial cutters (in Bangkok) often use the actual cleavage surface as the table, to save cutting labor. When re-cutting a “native” cut stone, test the table on a polishing lap to ensure that it is not the cleavage plane.
Design Notes: About any Tourmaline or Topaz design will work well. I prefer checker boards in darker materials.