Answer: Check out Faceting for Amateurs by Glenn and Martha Vargas. This book features an appendix that lists most gem materials and includes cutting and polishing information. It also has a section on unusual faceting materials.
Notes on Faceting Selected Exotic Gemstones
Here’s a summary of special notes for your exotic gemstones.
- Actinolite has very easy cleavage in two directions and requires care. Sharp corners will fray.
- Amblygonite has perfect cleavage in two directions.
- Celestite should be kept away from sulfite compounds. It’s extremely heat sensitive and best cut as a round gem.
- Dioptase is brittle. Its cleavage may mean trouble on course laps. Use only extra or ultra-fine laps. Use speed of 100 rpm or less for polish.
- Epidote is easy to cut and polish, but its cleavage may separate during heating. If the rough is a twin, the twinning planes can present problems.
- Leucite should pose no special problems if cut on fine laps at slow speeds. Keep it wet during polishing.
- Smithsonite should pose no problems if you avoid the three cleavage planes. Dopping heat with care.
Don’t forget that the International Gem Society (IGS) reference library includes a Gemstone Encyclopedia. This resource includes all kinds of information on lesser known gemstones and collector items.