AGA Round Brilliant Cut Grading Chart
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CUT CLASSES |
Class1A |
Class1B |
Class 2A |
Class 2B |
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American Ideal Cut |
International fine trade cut |
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Table % |
53-58% |
52-60% |
51.5-63% |
51-64% |
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Crown angle° |
34.0-34.7 |
33-35.1 |
32.1-35.8 |
31.6-36.4 |
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14-16.3% |
13.5-16.8% |
11.6-17.9% |
11.1-18.1% |
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42.8-43.2% |
42.5-43.5% |
42-44% |
41.5-44.9% |
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Girdle Thickness: |
Thin to Medium (1.0% to 3.0%) |
Very thin to Slightly thick (0.4% to 4.5%) |
Very thin to Slightly thick (0.4% to 4.5%) |
Very thin to Thick (0.4% to 5.5%) |
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Total depth %
Determined by
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58-62.3% |
58.3-62.99% |
<58.3% |
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NOT A PRIMARY |
Excellent -Very Good |
Excellent toGood |
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CUT CLASSES |
Class 3A |
Class 3B |
Class 4A |
Class 4B |
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US domestic average cut |
below average |
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Table % |
50.5-67% |
50-70% |
49-72% |
>72% |
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Crown angle° |
30.1-37.9 |
29.6-39.4 |
29-40.5 |
<29 |
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Crown height % |
9.6-19.3% |
8.5-20.5% |
7.8-21.8% |
<7.8% |
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Pavilion Depth % |
41-45.5% |
40.5-46% |
38-48% |
<38% |
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Girdle Thickness: |
Very thin to Very thick (0.4% to 7.0%) |
Extremely thin to Extremely thick (0.0% to >7.0%) |
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Total depth % |
<58.3% |
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Polish/Symmetry
NOT A PRIMARY |
Good -Fair |
Poor
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A diamond called a "Tolkowsky Cut" is only approximated by cut
1A. However, a "Tolkowsky Cut" is a very specifically calculated cut with
the following parameters:
Table 53.0%, Crown Angle 34.6, Crown Height 16.2%,
Girdle Thickness app 1.7%, Pavilion Depth 43.1%. Many
diamonds are improperly called "Tolkowsky Cut" when they are only approximating
the parameters Tolkowsky formulated.
Courtesy of D.S. Atlas, Accredited Gem Appraisers, © AGA 1998-2004
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