CUT GRADE

Proportions | Polish | Symmetry

HRD ANTWERP CUT GRADE

Definition of Cut Grade

The description of the Cut Grade on a grading report is subdivided into 3 grades: proportions, polish and
symmetry. Each grade is divided into 4 categories: Excellent, Very Good, Good and Fair.

The proportions are determinative for the brilliancy and the fire of the diamond.
The polish describes the finish of the facets.
The symmetry describes the variations of the different parameters which define the proportions.

HRD Antwerp Cut Grade

Proportions Polish Symmetry

Excellent Excellent Excellent

Very Good Very Good Very Good

Good Good Good

Fair Fair Fair

2 | Cut Grade
HRD ANTWERP CUT GRADE

Proportions

Determination of proportions

For a diamond to show an optimal combination of brilliancy and fire, it has to be polished with due attention
to the angles of inclination and proportional relations between the various parts of the stone. If the angles
and proportions are not optimal, this can lead to the appearance of one or more specific effects in the stone,
which are detrimental to its beauty. When grading the proportions of a polished diamond, the main issue is
therefore to evaluate if, and if so to what extent, these effects occur.

Parameters that can characterize the proportions for the round

brilliant
The crown angle ()
The pavilion angle ()
The proportion of the table width to the diameter (% t)
The proportion of the crown height to the diameter (% hc)
The proportion of the pavilion depth to the diameter (% hp)
The proportion of the girdle thickness to the diameter (% a)
The culet size (% culet)
The proportion of the total depth to the diameter (% td)
The sum of the crown- and pavilion angle (+)
The half length of the upper girdle facets
The half length of the lower girdle facets
The fish eye effect
The effect culet visible in the bezels

Profile of a diamond and the different parameters

AV. DIAMETER = 100 %
% TABLE WIDTH

% CROWN HEIGHT
CROWN ANGLE

% GIRDLE

PAVILION ANGLE

% TOTAL DEPTH
SUM &

% PAVILION DEPTH

% CULET
% LENGTH HALVES CROWN

% LENGTH HALVES PAVILION

Cut Grade | 3
HRD ANTWERP CUT GRADE

Proportions

Overview of the different parameters per category

Fair Good Very Good Excellent Very Good Good Fair

Crown angle () up to 25.9 26.0 to 27.9 28.0 to 31.9 32.0 to 36.0 36.1 to 37.7 37.8 to 40.0 40.1 and up

Pavilion angle () up to 38.4 38.5 to 39.5 39.6 to 40.5 40.6 to 41.8 41.9 to 42.1 42.2 to 43.1 43.2 and up

Table width up to 49.0 % 50.0 to 51.0 % 52.0 % 53.0 to 62.0 % 63.0 to 66.0 % 67.0 to 70.0 % 71.0 % and up

Crown height up to 8.5 % 9.0 to 10.5 % 11.0 to 11.5 % 12.0 to 16.0 % 16.5 to 18.0 % 18.5 to 19.5 % 20.0 % and up

Pavilion depth up to 39.5 % 40.0 to 41.0 % 41.5 to 42.5 % 43.0 to 44.5 % 45.0 % 45.5 to 46.5 % 47.0 % and up

Girdle up to 0.5 % 1.0 to 1.5 % 2.0 % 2.5 to 4.5 % 5.0 to 5.5 % 6.0 to 7.5 % 8.0 % and up

Culet size 0.0 to 0.9 % 1.0 to 1.9 % 2.0 to 3.9 % 4.0 % and up

Total depth up to 52.9 % 53.0 to 55.4 % 55.5 to 58.4 % 58.5 to 63.0 % 63.1 to 64.4 % 64.5 to 66.9 % 67.0 % and up

Sum and up to 67.9 68.0 to 69.9 70.0 to 72.4 72.5 to 77.0 77.1 to 79.4 79.5 to 80.4 80.5 and up

Half length crown up to 30.0 % 35.0 % 40.0 % 45.0 to 55.0 % 60.0 % 65.0 % 70.0 % and up

Half length pavilion up to 60.0 % 65.0 to 70.0 % 75.0 % 75.0 to 85.0 % 85.0 % 90.0 % 95.0 % and up

Fish-eye effect Excellent Good Fair

Culet in bezels Excellent Good Fair

If the measurement results are classified in two different categories, the lowest proportion grade is considered
to be the overall reading.

Effects that can be perceived when observing the stone perpen-

dicular to the table

Fish Eye: The reflection of the girdle is partially or completely visible in the table
(small pavilion angle and a large table width).

Culet visible in the bezels: The diamond shows an abnormal amount of scintillation, due to the culet
and the surrounding facets being visible through the bezels (a large total
depth and crown angle).

4 | Cut Grade
HRD ANTWERP CUT GRADE

Proportions

Relation Table Width - Crown Height

Table width (%)
50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70

19.5 38.0 38.5 39.1 39.7 40.3 40.9 41.6 42.2 42.9 43.6 44.3 45.0 45.7 46.5 47.3 48.1 48.9 49.8 50.6 51.5 52.4
19.0 37.2 37.8 38.4 39.0 39.6 40.2 40.8 41.5 42.1 42.8 43.5 44.3 45.0 45.8 46.5 47.4 48.2 49.0 49.9 50.8 51.7
18.5 36.5 37.1 37.6 38.2 38.8 39.4 40.1 40.7 41.4 42.1 42.8 43.5 44.2 45.0 45.8 46.6 47.4 48.3 49.1 50.0 51.0
18.0 35.8 36.3 36.9 37.5 38.0 38.7 39.3 39.9 40.6 41.3 42.0 42.7 43.5 44.2 45.0 45.8 46.6 47.5 48.4 49.3 50.2
17.5 35.0 35.5 36.1 36.7 37.3 37.9 38.5 39.1 39.8 40.5 41.2 41.9 42.6 43.4 44.2 45.0 45.8 46.7 47.6 48.5 49.4
17.0 34.2 34.8 35.3 35.9 36.5 37.1 37.7 38.3 39.0 39.7 40.4 41.1 41.8 42.6 43.4 44.2 45.0 45.9 46.7 47.6 48.6
16.5 33.4 34.0 34.5 35.1 35.7 36.3 36.9 37.5 38.2 38.8 39.5 40.2 41.0 41.7 42.5 43.3 44.1 45.0 45.9 46.8 47.7
16.0 32.6 33.1 33.7 34.2 34.8 35.4 36.0 36.7 37.3 38.0 38.7 39.4 40.1 40.9 41.6 42.4 43.3 44.1 45.0 45.9 46.8
15.5 31.8 32.3 32.9 33.4 34.0 34.6 35.2 35.8 36.4 37.1 37.8 38.5 39.2 40.0 40.7 41.5 42.4 43.2 44.1 45.0 45.9
Crown height (%)

15.0 31.0 31.5 32.0 32.6 33.1 33.7 34.3 34.9 35.5 36.2 36.9 37.6 38.3 39.0 39.8 40.6 41.4 42.3 43.2 44.1 45.0
14.5 30.1 30.6 31.1 31.7 32.2 32.8 33.4 34.0 34.6 35.3 35.9 36.6 37.3 38.1 38.9 39.6 40.5 41.3 42.2 43.1 44.0
14.0 29.2 29.7 30.3 30.8 31.3 31.9 32.5 33.1 33.7 34.3 35.0 35.7 36.4 37.1 37.9 38.7 39.5 40.3 41.2 42.1 43.0
13.5 28.4 28.9 29.4 29.9 30.4 31.0 31.5 32.1 32.7 33.4 34.0 34.7 35.4 36.1 36.9 37.6 38.5 39.3 40.2 41.1 42.0
13.0 27.5 28.0 28.4 29.0 29.5 30.0 30.6 31.2 31.8 32.4 33.0 33.7 34.4 35.1 35.8 36.6 37.4 38.2 39.1 40.0 40.9
12.5 26.6 27.0 27.5 28.0 28.5 29.1 29.6 30.2 30.8 31.4 32.0 32.7 33.3 34.0 34.8 35.5 36.3 37.1 38.0 38.9 39.8
12.0 25.6 26.1 26.6 27.1 27.6 28.1 28.6 29.2 29.7 30.3 31.0 31.6 32.3 33.0 33.7 34.4 35.2 36.0 36.9 37.7 38.7
11.5 24.7 25.1 25.6 26.1 26.6 27.1 27.6 28.1 28.7 29.3 29.9 30.5 31.2 31.9 32.6 33.3 34.1 34.9 35.7 36.6 37.5
11.0 23.7 24.2 24.6 25.1 25.6 26.1 26.6 27.1 27.6 28.2 28.8 29.4 30.1 30.7 31.4 32.2 32.9 33.7 34.5 35.4 36.3
10.5 22.8 23.2 23.6 24.1 24.5 25.0 25.5 26.0 26.6 27.1 27.7 28.3 28.9 29.6 30.3 31.0 31.7 32.5 33.3 34.1 35.0
10.0 21.8 22.2 22.6 23.1 23.5 24.0 24.4 24.9 25.5 26.0 26.6 27.1 27.8 28.4 29.1 29.7 30.5 31.2 32.0 32.8 33.7
9.5 20.8 21.2 21.6 22.0 22.4 22.9 23.4 23.8 24.3 24.9 25.4 26.0 26.6 27.2 27.8 28.5 29.2 29.9 30.7 31.5 32.3
9.0 19.8 20.2 20.6 21.0 21.4 21.8 22.2 22.7 23.2 23.7 24.2 24.8 25.3 25.9 26.6 27.2 27.9 28.6 29.4 30.1 31.0

Excellent Very Good Good Fair Bezel angle ()

Table width (%)

50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70
60
19.5 38.0 38.5 39.1 39.7 40.3 40.9 41.6 42.2 42.9 43.6 44.3 45.0 45.7 46.5 47.3 48.1 48.9 49.8 50.6 51.5 52.4
19.0 37.2 37.8 38.4 39.0 39.6 40.2 40.8 41.5 42.1 42.8 43.5 44.3 45.0 45.8 46.5 47.4 48.2 49.0 49.9 50.8 51.7
18.5 36.5 37.1 37.6 38.2 38.8 39.4 40.1 40.7 41.4 42.1 42.8 43.5 44.2 45.0 45.8 46.6 47.4 48.3 49.1 50.0 51.0
18.0 35.8 36.3 36.9 37.5 38.0 38.7 39.3 39.9 40.6 41.3 42.0 42.7 43.5 44.2 45.0 45.8 46.6 47.5 48.4 49.3 50.2
17.5 35.0 35.5 36.1 36.7 37.3 37.9 38.5 39.1 39.8 40.5 41.2 41.9 42.6 43.4 44.2 45.0 45.8 46.7 47.6 48.5 49.4
Pavilion angle:
17.0 34.2 34.8 35.3 35.9 36.5 37.1 37.7 38.3 39.0 39.7 40.4 41.1 41.8 42.6 43.4 44.2 45.0 45.9 46.7 47.6 48.6
16.5 33.4 34.0 34.5 35.1 35.7 36.3 36.9 37.5 38.2 38.8 39.5 40.2 41.0 41.7 42.5 40.6
minimum 43.3 44.1 45.0 45.9 46.8 47.7
16.0 32.6 33.1 33.7 34.2 34.8 35.4 36.0 36.7 37.3 38.0 38.7 39.4 maximum
40.1 40.9 41.6 41.1
42.4 43.3 44.1 45.0 45.9 46.8
15.5 31.8 32.3 32.9 33.4 34.0 34.6 35.2 35.8 36.4 37.1 37.8 38.5 39.2 40.0 40.7 41.5 42.4 43.2 44.1 45.0 45.9
Crown height (%)

15.0 31.0 31.5 32.0 32.6 33.1 33.7 34.3 34.9 35.5 36.2 36.9 37.6 38.3 39.0 39.8 40.6 41.4 42.3 43.2 44.1 45.0
14.5
14.5 30.1 30.6 31.1 31.7 32.2 32.8 33.4 34.0 34.6 35.3 35.9
35.9 36.6 37.3 38.1 38.9 39.6 40.5 41.3 42.2 43.1 44.0
14.0 29.2 29.7 30.3 30.8 31.3 31.9 32.5 33.1 33.7 34.3 35.0 35.7 36.4 37.1 37.9 38.7 39.5 40.3 41.2 42.1 43.0
13.5 28.4 28.9 29.4 29.9 30.4 31.0 31.5 32.1 32.7 33.4 34.0 34.7 35.4 36.1 36.9 37.6 38.5 39.3 40.2 41.1 42.0
13.0 27.5 28.0 28.4 29.0 29.5 30.0 30.6 31.2 31.8 32.4 33.0 33.7 34.4 35.1 35.8 36.6 37.4 38.2 39.1 40.0 40.9
12.5 26.6 27.0 27.5 28.0 28.5 29.1 29.6 30.2 30.8 31.4 32.0 32.7 33.3 34.0 34.8 35.5 36.3 37.1 38.0 38.9 39.8
12.0 25.6 26.1 26.6 27.1 27.6 28.1 28.6 29.2 29.7 30.3 31.0 31.6 32.3 33.0 33.7 34.4 35.2 36.0 36.9 37.7 38.7
11.5 24.7 25.1 25.6 26.1 26.6 27.1 27.6 28.1 28.7 29.3 29.9 30.5 31.2 31.9 32.6 33.3 34.1 34.9 35.7 36.6 37.5
11.0 23.7 24.2 24.6 25.1 25.6 26.1 26.6 27.1 27.6 28.2 28.8 29.4 30.1 30.7 31.4 32.2 32.9 33.7 34.5 35.4 36.3
10.5 22.8 23.2 23.6 24.1 24.5 25.0 25.5 26.0 26.6 27.1 27.7 28.3 28.9 29.6 30.3 31.0 31.7 32.5 33.3 34.1 35.0
10.0 21.8 22.2 22.6 23.1 23.5 24.0 24.4 24.9 25.5 26.0 26.6 27.1 27.8 28.4 29.1 29.7 30.5 31.2 32.0 32.8 33.7
9.5 20.8 21.2 21.6 22.0 22.4 22.9 23.4 23.8 24.3 24.9 25.4 26.0 26.6 27.2 27.8 28.5 29.2 29.9 30.7 31.5 32.3
9.0 19.8 20.2 20.6 21.0 21.4 21.8 22.2 22.7 23.2 23.7 24.2 24.8 25.3 25.9 26.6 27.2 27.9 28.6 29.4 30.1 31.0

Excellent Very Good Good Fair Bezel angle ()

Cut Grade | 5
HRD ANTWERP CUT GRADE

Proportions

Description of the girdle and influence on the proportions

Description of the girdle Measured value Proportion Grade

Extremely thin 0.0 0.5 % Fair

Very thin 1.0 1.5 % Good

2.0 % Very Good

Thin
2.5 %
Excellent
3.0 4.5 %
Medium
5.0 %
Very Good
5.5 %
Thick
6.0 %
Good
Very thick 6.5 7.5 %

Extremely thick 8.0 % and up Fair

The influence of the culet size on the proportions

Description of the culet Culet Size Proportion Grade

Pointed 0.0 % (< 0.033 mm) Excellent

0.1 % (0.033 mm) 0.9 %

1.0 1.9 % Very Good

2.0 3.9 % Good

Large 4.0 % and up Fair

6 | Cut Grade
HRD ANTWERP CUT GRADE

Polish

Polish defines all external characteristics of the diamond. These characteristics are mostly the result of
polishing the diamond.

The characteristics being graded

Scratches
Percussion figures
Beard
Polishing lines
Abraded facet edges
Pit
Nick
Burn marks
Laser marks
Extra facets
Naturals

Description of the polish

Polish Observation with loupe 10x

Excellent Characteristics, not or very difficult to find with a loupe 10x

Very Good Characteristics, difficult to find with a loupe 10x

Good Characteristics, easy to find with a loupe 10x

Fair Characteristics, very easy to find with a loupe 10x

Cut Grade | 7
HRD ANTWERP CUT GRADE

Symmetry

Determination of symmetry
The symmetry describes the variations of the different parameters which define the proportions.

Measurable deviations

Symmetry-deviations Excellent Very Good Good Fair

Unroundness < 1.0 % < 2.0 % < 4.0 % 4.0 % and up

Variation in crown height < 1.0 % < 2.0 % < 5.0 % 5.0 % and up
Variation in pavilion depth < 2.0 % < 3.0 % < 6.0 % 6.0 % and up
Table out of centre < 1.0 % < 2.0 % < 5.0 % 5.0 % and up
Culet out of centre < 1.0 % < 2.0 % < 5.0 % 5.0 % and up
Table and culet out of centre < 1.0 % < 2.0 % < 5.0 % 5.0 % and up
Variation on the table width < 2.0 % < 4.0 % < 8.0 % 8.0 % and up
Single cut effect < 0.8 % < 2.0 % < 4.0 % 4.0 % and up
Deviation on the crown angles < 2.0 < 4.0 < 8.0 8.0 and up
Deviation on the pavilion angles < 1.0 < 2.0 < 4.0 4.0 and up
Deviation on the angles of the lower girdle facets < 1.0 < 2.0 < 4.0 4.0 and up

Not measurable deviations

Deviation of the bezels

Deviation of the pavilions
Cone-shaped girdle
Visual Misalignment
deviations Girdle partly faceted
Bow tie effect
Deviation on the girdle thickness (on max & min)
Deviation on the angles of the upper girdle facets

Information about the effects

Single Cut effect: The diamond looks as if it has less facets than are really present. A single cut effect is caused
by the angles of the bezels / pavilions and the halves of the bezels / pavilions side.
Bow tie effect: Through the crown side, two dark zones in the shape of a bow tie can be seen.

8 | Cut Grade
HRD ANTWERP CUT GRADE

Symmetry deviations

Measurable deviations

1. Girdle outline not 15. Crown side not aligned

circular to pavilion side

2. Slanting table 16. Cone-shaped girdle

3. Sloping girdle 17. Girdle partly faceted

20. Pavilion facets not

4. Culet out of centre
symmetrical

22. Pavilion facets not

5. Table out of centre
pointing up

6. Table and culet out

23. Deviation on the bezel
of centre in opposite
angles
direction

7. Table and/or star 24. Deviation on the

facets not symmetrical pavilion angles

25. Deviation on the angles

10. Bezels not symmetrical of the upper girdle
facets

26. Deviation on the angles

12. Crown facets not
of the lower girdle
pointing up
facets

13. Varying girdle

BOW-TIE
thickness

14. Single cut effect (due

to alternating girdle
thickness)

Cut Grade | 9
HRD ANTWERP CUT GRADE

Symmetry deviations

Different symmetry deviations of the girdle

Perfect symmetry average(H) =

2.5%

2.5% (Halves)
2.5% (Bezels)

1% (Valley)
average(B) =
2.5%

variation girdle height (B & H) =

max (B&H) min (B&H) = 2.5 2.5 = 0%

variation girdle height (V) =

max (V) min (V) = 1 1 = 0%

variation girdle height = max [variation girdle height (B & H) & variation girdle height (V)] = 0%

single cut = average (H) average (B) = 2.5 2.5 = 0% (<0.8%) => Exc

Single cut effect average(H) =

2.7%

2.7% (Halves)
2.3% (Bezels)

1% (Valley)
average(B) =
2.3%

variation girdle height (B & H) =

max (B&H) min (B&H) = 2.7 2.3 = 0.4%

variation girdle height (V) =

max (V) min (V) = 1 1 = 0%

variation girdle height = max [variation girdle height (B & H) & variation girdle height (V)] = 0.4%

single cut = average (H) average (B) = 2.7 2.3 = 0.4% (<0.8%) => Exc

Variation girdle height average(H) =

2.6%

average(B) =
1.5%
2.5%
3.4%

2.5%

2.5%

variation girdle height (B & H) =

max (B&H) min (B&H) = 3.4 2.5 = 0.9%

variation girdle height (V) =

max (V) min (V) = 1.5 1.5 = 0%

variation girdle height = max [variation girdle height (B & H) & variation girdle height (V)] = 0.9%

single cut = average (H) average (B) = 2.6 2.5 = 0.1% (<0.8%) => Exc

Variation girdle height average(H) =

2.5%
Hmax = 3%
Hmin = 2%
Vmax = 1.5%

average(B) =
Vmin = 0.5%

Bmin = 2%

Bmax = 3%

2.5%
2.5%

1%

2.5%

variation girdle height (B & H) =

max (B&H) min (B&H) = 3 2 = 1%

variation girdle height (V) =

max (V) min (V) = 1.5 0.5 = 1%

variation girdle height = max [variation girdle height (B & H) & variation girdle height (V)] = 1%

single cut = average (H) average (B) = 2.5 2.5 = 0% (<0.8%) => Exc

Illustrations: WTOCD

10 | Cut Grade
HRD ANTWERP CUT GRADE

Conclusion

The proportion grade is based on the average of the measured values. If there is a large deviation on one or
more values, the beauty of the diamond can be influenced. The table below shows the influence of symmetry
and/or polish on the final proportion grade.

Pol. / Sym.
Excellent Very Good Good Fair
Proportions

Excellent Excellent Excellent Very Good Good

Very Good Very Good Very Good Very Good Good

Good Good Good Good Good

Fair Fair Fair Fair Fair

Cut Grade | 11
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