Forums Beginner Questions Changing diagram angles


  • Changing diagram angles

    Posted by brellan217 on October 23, 2018 at 2:57 pm

    I want to make my pieces more vibrant and beautiful. I know there is a way to mathematically change facet angles based on R.I. However, I am at a complete loss as to how to do this.

    Say, for example, I have a diagram for quartz with a RI of around 1.5. My C1 angles are 49.6. I want to cut a beryl with a RI of around 1.6. How do I change that 49.6 specific to quartz to something more appropriate for the RI of the beryl to maximize light refraction?

    I would like to be able to create an Excel file to easily change my refractive indices for me. Is there a formula that works every time?

    Thanks all!

    Gregory Hays replied 4 years, 4 months ago 6 Members · 7 Replies
  • 7 Replies
  • scottwkelley

    October 23, 2018 at 3:44 pm
  • Alan Balmer

    October 23, 2018 at 4:38 pm

    There’s an even easier way, if you have GemCad. You can change the angle on one facet, and the program will tangent ratio the entire half (crown or pavilion) of the design. The companion GemRay program will help you find the angles which perform best. The newer Gem Cut Studio program will do it all, but I haven’t yet spent much time with it.

  • brellan217

    October 23, 2018 at 11:22 pm

    Thank you for the replies. I am going to look into the gem cut software. I couldn’t use the gem ray or gem cad software because it was confusing to me. Hoping it helps!

    I tried a Portuguese cut that I transposed once before. The stone came out dead and lifeless. Like a window you could see right through :(. I’m hoping not to repeat that so these answers may help.

  • Dennis Anderson in sunny Southern California

    October 26, 2018 at 12:52 am

    You might find that changing the angles from Quartz to Beryl are so close that it really doesn’t make much difference to do it. The previous post that said: Try this will give you a way to make changes to as design to use with an increase of the RI to a “brighter” stone. Don’t try to push this too far up the RI chain as high RI materials may not need to be pushed to the last degree to give you a great stone. Learning to use the design software programs that are available is desirable to verify that changes really will be workable. Don’t try to push high RI designs down to low RI minerals as most won’t work well.
    Dennis Anderson.

  • mike56

    March 5, 2020 at 9:53 pm

    I have also an issue, I try to make a pear cut with ratio 1/1.4 with a CZ ,all the diagrams that I found are for ri 1.54. All angle are they to high above critical ? they look ok with gemcad raytrace with little change on the crown ( increase angle ) ..but I m afraid , if anybody have already one for CZ …could be much more easier for me …Main pavillon 41,50 , crown from 33 to 10 degrees …if it help…I attach the design

  • Gregory Hays

    March 6, 2020 at 11:05 pm

    Like Dennis has said, The Ri of quartz at 1.54 and beryl at 1.58 are not enough to warrant a change in angles. More than likely a design change may be the answer.
    I find on beryl leaving the pavillion angles as stated for quartz and tangent ratio the crown main angles down 1 degree helps on beryl. Just my opinion though.

  • Gregory Hays

    March 6, 2020 at 11:48 pm

    Not sure if I understand completely. The uploaded design is 1.33 not 1.4. It is designed to work with quartz with an RI of 1.54, CZ has a very high RI and can be cut in almost all designs.
    In any case I ran it in Gemray and bumped it up little in performance. See attached.

    I like the alternate design better personally on lighter saturated material. It is a Robert Long design run through GemRay for higher RI Cubic Zirconia.

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