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This document shows what criteria DiamCalc uses for diamond grading according to HRD system
The data listed here is not an official HRD data. It is provided
here for possibility to check its suitability for your purposes.
OctoNus software recommends that you check the data and modify
it as necessary as described here
before using DiamCalc to grade diamonds for commercial purposes.
| Brilliant Cut |
| Parameter name |
Meaning |
Very good |
Good |
| UpAngle ° |
Crown angle |
30.7 - 37.7 |
27.0 - 40.6 |
| DownAngle ° |
Pavilion angle |
39.60 - 42.25 |
38.45 - 43.15 |
| GirdleHeight_GIA |
Girdle thickness |
Thin - Medium |
Thin - Very thick |
| Table % |
Table diameter |
52.8 - 66.2 |
50.6 - 70.2 |
| GirdleRatio |
Ratio of max/min diameters |
0.980 - 1.020 |
0.980 - 1.020 |
| Pavilion % |
N/A |
10 - 25 |
10 - 25 |
| UpHeight_GIA % |
Crown height |
10.8 - 16.2 |
8.8 - 18.2 |
| Kozibe ° |
Kozibe effect |
6 - 91 |
0 - 91 |
| FishEye % |
FishEye effect |
0 - 100 |
0 - 100 |
| FullHeight % |
Total height |
55.5 - 63.9 |
53.0 - 66.9 |
| Culet_mm |
Culet size |
Pointed - Medium |
Pointed - Slightly large |
| GirdleDeviation % |
Ratio of max/min diameters |
-2 - +2 |
-2 - +2 |
| GirdleHeight_GIA, % (translation table for girdle thickness)
|
| Girdle description
|
Values |
| Extremely thin |
less than 0.75 |
| Very thin |
0.75 - 1.75 |
| Thin |
1.75 - 2.75 |
| Medium |
2.75 - 4.75 |
| Thick |
4.75 - 6.25 |
| Very thick |
6.25 - 7.75 |
| Extremely thick |
more than 7.75 |
| Culet_mm, mm (translation table for culet size) |
| Culet description |
Values |
| Pointed |
less than 0.010 |
| Very small |
0.010 - 0.020 |
| Small |
0.020 - 0.030 |
| Medium |
0.030 - 0.090 |
| Slightly large |
0.090 - 0.220 |
| Large |
0.220 - 0.400 |
| Very large |
0.400 - 0.800 |
| Extremely large |
more than 0.800 |
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