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Question for Mr. Holloway - change 0.4 degrees and grades drop from ex to gd

Discussion in 'RockyTalky' started by guy57, May 10, 2001.

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  1. guy57
    Rough_Rock

    Messages:
    8
    Joined:
    May 26, 2001
    by guy57 » May 10, 2001
    Mr. Holloway,Here's a stone that I'm looking at:GIA cert
    round brilliant cut
    E color
    VS2 clarity (light feathers on the peripheral)
    1.58ct
    56% table
    61.8% depth
    35.8 degrees crown angle
    40.4 degrees pavillon angle
    very good symmetry and polish I used the HCA and got 0.9. The ratings are ex-ex-ex-vg.However, I tried to play with the angles a little and found that if I use a pavillon angle of 40.8 degrees, the total score becomes 3.9 and ratings are gd-gd-gd-vg. Can you help me understand why such a small change in the pavillon angle (0.4 degrees) would change so much? Further, I understand that the Sarin report gives only averages, what should I do to ensure that the stone behaves more like 0.9 stone and not a 3.9 stone?Thanks for your help!
     
    


    


  2. guy57
    Rough_Rock

    Messages:
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    Joined:
    May 26, 2001
    by guy57 » May 10, 2001
    Thanks for replying!Enjoy Italy! If you get a chance, don't miss Cinque Terre, by La Spezia.
     
  3. pricescope
    Ideal_Rock

    Messages:
    8,266
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    Dec 31, 1999
    by pricescope » May 11, 2001
    Guy57,Garry is traveling now and I'm not sure that he will be able to answer your question soon.I tried answering myself though in the other thread...
     
  4. Garry H (Cut Nut)
    Super_Ideal_Rock
    Trade

    Messages:
    14,538
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    by Garry H (Cut Nut) » May 11, 2001
    hi from italy [​IMG]yes the pavilion causes 5 times the effect of crown angle or table size.even if that stone is off symmetry it will still be very good, but hard to explain with time i have now.good you are using angles not %'s too
    garry h
     
    


    


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