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GIA system appraiser
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This
document shows what criteria DiamCalc uses
for diamond grading according to GIA system.
The
data listed here is not an official GIA
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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E-VG
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G
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F
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UpAngle
°
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Crown
angle
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34
- 35
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32
- 36
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30
- 37
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DownHeight_GIA
%
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Pavilion
depth
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43
- 43.5
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42
- 44
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41
- 46
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GirdleHeight_mm
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Girdle
thickness
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Medium
-
Slightly thick
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Thin
-
Thick
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Very
thin -
Very thick
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Table
%
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Table
diameter
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53
- 60
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52
- 64
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51
- 70
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GirdleRatio
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Ratio
of max/min diameters
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0.98
- 1.02
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0.98
- 1.02
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0.98
- 1.02
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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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10
- 25
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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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Pointed
- 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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-2
- +2
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GirdleHeight_mm,
mm
(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 0.08
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Very
thin
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0.08
- 0.12
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Thin
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0.12
- 0.15
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Medium
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0.15
- 0.20
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Thick
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0.20
- 0.33
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Very
thick
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0.33
- 0.40
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Extremely
thick
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more
than 0.40
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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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