Topaz

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
Dispersion: Medium (.014)
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

Design Links:
Cornered - This is great for Electric Blue rough if you have a piece that will work...
4 Way Stop - Nice in London Blue
Gram Princess - Nice in about any color

Rough Links:
Topaz - Index of Topaz Rough
Electric Blue - London Blue Topaz, Electric Blue Topaz
Guerro - Guerro Topaz from Mexico
Imperial - Imperial Topaz from Brazil
Sierra Blue - Sierra Blue Topaz
Topaz - Swiss Blue Topaz, Sky Blue Topaz, Light Blue Topaz, White Topaz Preforms in parcels, White Tumbled Topaz from Africa, , Brazilian Topaz Parcels mixed colors

Cut Stone Links:
Topaz - Faceted Topaz

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E-mail to inquire or order: jeff@faceters.com