Iolite Faceting Information
A guide to Iolite Faceting Information. Essential information on Iolite faceting that includes tips on cuts and polishes together with helpful details.
Color: Blue/purple and yellow with violet and/or gray undertones
Moh's Hardness: 7-7.5
Refractive Index: 1.53-1.55
Critical Angle: 40.81°
Specific Gravity: 2.58-2.66
Cleavage: Distinct in 3 directions
Fracture: Uneven, conchoidal, brittle
Dispersion: .017
Heat Sensitivity: Can be in my experience
Trichroic: Strong (yellow to dark blue-violet to pale-blue)
Birefringence (double refraction): Weak to medium (.008-.012)
Crystal Structure: Orthorhombic
Treatments: Generally none
What I prefer to polishing with: Cerium oxide on a Tin lap
Jeff's Comments: Very difficult to find quality rough. Iolite has fairly strong cleavage in one direction and fractures along this plane are common. The other cleavage planes usually don't create problems, but occasionally cause difficulties in polishing. Some material is light and some is very saturated, match the design to the saturation level.
Design Notes: About any Quartz designs will work well.
Design Links: Cornered - Nice for darker stones
Easy Emerald - Good for color
Jeff R. Graham
The late Jeff Graham was a prolific faceter, creator of many original faceting designs, and the author of several highly-regarded instructional faceting books such as Gram Faceting Designs.
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