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HRD system appraiser
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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.
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Brilliant
Cut
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Parameter
name
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Meaning
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Very
good
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Good
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UpAngle
°
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Crown angle
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30.7
- 37.7
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27.0
- 40.6
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DownAngle
°
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Pavilion
angle
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39.60
- 42.25
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38.45
- 43.15
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GirdleHeight_GIA
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Girdle thickness
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Thin
- Medium
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Thin
- Very thick
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Table
%
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Table diameter
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52.8
- 66.2
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50.6
- 70.2
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GirdleRatio
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Ratio of
max/min diameters
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0.980
- 1.020
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0.980
- 1.020
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Pavilion
%
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N/A
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10
- 25
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10
- 25
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UpHeight_GIA
%
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Crown height
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10.8
- 16.2
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8.8
- 18.2
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Kozibe
°
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Kozibe effect
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6
- 91
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0
- 91
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FishEye
%
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FishEye
effect
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0
- 100
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0
- 100
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FullHeight
%
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Total height
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55.5
- 63.9
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53.0
- 66.9
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Culet_mm
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Culet size
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Pointed
- Medium
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Pointed
- Slightly large
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GirdleDeviation
%
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Ratio of
max/min diameters
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-2
- +2
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-2
- +2
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GirdleHeight_GIA,
%
(translation table for girdle thickness)
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Girdle
description
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Values
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Extremely
thin
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less
than 0.75
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Very
thin
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0.75
- 1.75
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Thin
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1.75
- 2.75
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Medium
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2.75
- 4.75
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Thick
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4.75
- 6.25
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Very
thick
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6.25
- 7.75
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Extremely
thick
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more
than 7.75
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Culet_mm,
mm (translation table for culet size)
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Culet
description
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Values
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Pointed
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less
than 0.010
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Very
small
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0.010
- 0.020
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Small
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0.020
- 0.030
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Medium
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0.030
- 0.090
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Slightly
large
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0.090
- 0.220
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Large
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0.220
- 0.400
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Very
large
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0.400
- 0.800
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Extremely
large
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more
than 0.800
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