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Cutting from instructions



If I have instructions and they are designed for lets say quartz RI 1,54. And I have to cut sapphire.
How do I know the angles? i know that you cut quartz 2 degrees deeper, but I have red here that sometimes you can use same degrees for lets say 1,54-2,00 RI with that particular instruction.

If the instructions do not tell that you can use same degrees for 1,54-2,00 what shall I do so I do not cut the gem wrong?

Thank you.


You can use Snell’s Law to compute the critical angle or angle of total reflection if you know the refractive index of your material. See this little treatise: In simpler terms … add 2 degrees to the crown and pavilion angles for diamonds (40.8 degrees optimum pavilion angle for diamond + 2 = 42.8 [43 will work too] and 35 degrees optimum crown angle for diamond + 2 = 37). Enjoy. :smiley: