The tables below show the AGA Cut Grading system for round diamonds developed by D. S. Atlas and his laboratory Accredited Gem Appraisers. This system has been adopted by the National Association of Jewelry Appraisers (NAJA).
CUT CLASSES |
Class1A
|
Class1B
|
Class 2A
|
Class 2B
|
|
American Ideal Cut
|
International fine trade cut
|
 |
 |
Table % |
53-58%
|
52-60%
|
51.5-63%
|
51-64%
|
 |
 |
Crown angle° |
34.0-34.7
|
33-35.1
|
32.1-35.8
|
31.6-36.4
|
 |
 |
Crown height % |
14-16.3%
|
13.5-16.8%
|
11.6-17.9%
|
11.1-18.1%
|
 |
 |
Pavilion Depth % |
42.8-43.2%
|
42.5-43.5%
|
42-44%
|
41.5-44.9%
|
 |
 |
Girdle Thickness:
Word descriptions |
Thin to Medium (1.0% to 3.0%)
Medium to Slightly thick (1.7% to 4.5%)
|
Very thin to Slightly thick (0.4% to 4.5%)
Thin to Slightly thick (1.0% to 4.5%)
|
Very thin to Slightly thick (0.4% to 4.5%)
|
Very thin to Thick (0.4% to 5.5%)
|
 |
 |
Total depth %
Determined by
factors already
considered above |
58-62.3%
|
58.3-62.99%
|
<58.3%
>63%
|
 |
 |
Polish/Symmetry
NOT A PRIMARY
DETERMINING
FACTOR |
Excellent –Very Good
|
Excellent toGood
|
 |
 |
CUT CLASSES |
Class1A
|
|
American Ideal Cut
|
Table % |
53-58%
|
Crown angle° |
34.0-34.7
|
Crown height % |
14-16.3%
|
Pavilion Depth % |
42.8-43.2%
|
Girdle Thickness:
Word descriptions |
Thin to Medium (1.0% to 3.0%)
Medium to Slightly thick (1.7% to 4.5%)
|
Total depth %
Determined by
factors already
considered above |
58-62.3%
|
Polish/Symmetry
NOT A PRIMARY
DETERMINING
FACTOR |
Excellent -Very Good
|
CUT CLASSES |
Class1B
|
|
American Ideal Cut
|
Table % |
52-60%
|
Crown angle° |
33-35.1
|
Crown height % |
13.5-16.8%
|
Pavilion Depth % |
42.5-43.5%
|
Girdle Thickness:
Word descriptions |
Very thin to Slightly thick (0.4% to 4.5%)
Thin to Slightly thick (1.0% to 4.5%)
|
Total depth %
Determined by
factors already
considered above |
58.3-62.99%
|
Polish/Symmetry
NOT A PRIMARY
DETERMINING
FACTOR |
Excellent -Very Good
|
CUT CLASSES |
Class 2A
|
|
International fine trade cut
|
Table % |
51.5-63%
|
Crown angle° |
32.1-35.8
|
Crown height % |
11.6-17.9%
|
Pavilion Depth % |
42-44%
|
Girdle Thickness:
Word descriptions |
Very thin to Slightly thick (0.4% to 4.5%)
|
Total depth %
Determined by
factors already
considered above |
<58.3%
>63%
|
Polish/Symmetry
NOT A PRIMARY
DETERMINING
FACTOR |
Excellent toGood
|
CUT CLASSES |
Class 2B
|
|
International fine trade cut
|
Table % |
51-64%
|
Crown angle° |
31.6-36.4
|
Crown height % |
11.1-18.1%
|
Pavilion Depth % |
41.5-44.9%
|
Girdle Thickness:
Word descriptions |
Very thin to Thick (0.4% to 5.5%)
|
Total depth %
Determined by
factors already
considered above |
<58.3%
>63%
|
Polish/Symmetry
NOT A PRIMARY
DETERMINING
FACTOR |
Excellent toGood
|
CUT CLASSES |
Class 3A
|
Class 3B
|
Class 4A
|
Class 4B
|
|
US domestic average cut
|
below average
|
 |
 |
Table % |
50.5-67%
|
50-70%
|
49-72%
|
>72%
<49%
|
 |
 |
Crown angle° |
30.1-37.9
|
29.6-39.4
|
29-40.5
|
<29
>40.5
|
 |
 |
Crown height % |
9.6-19.3%
|
8.5-20.5%
|
7.8-21.8%
|
<7.8%
>21.8%
|
 |
 |
Pavilion Depth % |
41-45.5%
|
40.5-46%
|
38-48%
|
<38%
>48%
|
 |
 |
Girdle Thickness:
Word descriptions |
Very thin to Very thick (0.4% to 7.0%)
|
Extremely thin to Extremely thick (0.0% to >7.0%)
|
 |
 |
Total depth % |
<58.3%
>63%
|
 |
 |
Polish/Symmetry
NOT A PRIMARY
DETERMINING
FACTOR |
Good –Fair
|
Poor
|
 |
 |
CUT CLASSES |
Class 3A
|
|
US domestic average cut
|
Table % |
50.5-67%
|
Crown angle° |
30.1-37.9
|
Crown height % |
9.6-19.3%
|
Pavilion Depth % |
41-45.5%
|
Girdle Thickness:
Word descriptions |
Very thin to Very thick (0.4% to 7.0%)
|
Total depth % |
<58.3%
>63%
|
Polish/Symmetry
NOT A PRIMARY
DETERMINING
FACTOR |
Good -Fair
|
CUT CLASSES |
Class 3B
|
|
US domestic average cut
|
Table % |
50-70%
|
Crown angle° |
29.6-39.4
|
Crown height % |
8.5-20.5%
|
Pavilion Depth % |
40.5-46%
|
Girdle Thickness:
Word descriptions |
Very thin to Very thick (0.4% to 7.0%)
|
Total depth % |
<58.3%
>63%
|
Polish/Symmetry
NOT A PRIMARY
DETERMINING
FACTOR |
Good -Fair
|
CUT CLASSES |
Class 4A
|
|
below average
|
Table % |
49-72%
|
Crown angle° |
29-40.5
|
Crown height % |
7.8-21.8%
|
Pavilion Depth % |
38-48%
|
Girdle Thickness:
Word descriptions |
Extremely thin to Extremely thick (0.0% to >7.0%)
|
Total depth % |
<58.3%
>63%
|
Polish/Symmetry
NOT A PRIMARY
DETERMINING
FACTOR |
Poor
|
CUT CLASSES |
Class 4B
|
|
below average
|
Table % |
>72%
<49%
|
Crown angle° |
<29
>40.5
|
Crown height % |
<7.8%
>21.8%
|
Pavilion Depth % |
<38%
>48%
|
Girdle Thickness:
Word descriptions |
Extremely thin to Extremely thick (0.0% to >7.0%)
|
Total depth % |
<58.3%
>63%
|
Polish/Symmetry
NOT A PRIMARY
DETERMINING
FACTOR |
Poor
|
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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