Brilliant Cut Diamonds..

Brilliant Cut Diamond

Certified Diamonds

Diam Help

4CS

Cut
The most popular cut is the modern round brilliant:

Round Brilliant Round Brilliant Diamond top view Round Brilliant Round Brilliant Diamond side view

Round Brilliant

Round Brilliant Facets

The standard brilliant comprises:

Upper:

1 Table facet
8 Star facets
8 Kite or Upper Main Facets
16 Upper Girdle facets

Total facets: 33 Crown Facets

Girdle:

This is the waist band in the middle, and is sometimes faceted.

Pavilion:

8 Pavilion
16 Lower Girdle
1 Culet

Total facets: 25 Pavilion Facets

Thus there are 58 facets in total.

There are many ideal cuts or sets of proportions and facet angles for the round brilliant cut. Below are the proportions for a brilliant in percentages of girdle diameter according to the IDC (International Diamond Council formed in 1979)

Criteria Unusual Good Very Good Good Unusual

Crown Angle < 26.9 27.0 to 30.6 30.7 to 37.7 37.8 to 40.6 40.7 +

Pavilion Angle < 38.4 38.5 to 39.5 39.6 to 42.2 42.3 to 43.1 43.2 +

Table width 71%+ 70% to 67% 66% to 53% 52% to 51% < 50%

Crown height < 8.5% 9% to 10.5% 11% to 16% 16.5% to 18% 18.5% +

Girdle thickness extremely thin very thin thin & medium thick & V thick extremely thick

Pavilion Depth (for pointed culet) < 39.5% 40% to 41% 41.5% to 45% 45.5% to 46.5% 47%+

Culet Size pointed to 1.9% 2% to 3.9% 4%+

Total depth < 52.9% 53.0% to 55.4% 55.5% to 63.9% 64% to 66.9% 67.0%+

Cut Ratio

It can be seen therefore that a ratio can be realised for any given brilliant cut diamond, and which when calculated, will yield its deviation from the 100% brilliance of the Eulitz Cut (mathematically perfect). We can calculate this for you when you purchase a diamond from us and it indicates mathematically how well your diamond has been cut. We generally reject stones that fall below 9% deviation. You might think this is a hard line approach, but we aim to supply you with diamonds that exceed your expectations.

Types of Brilliant cut:

The 'Ideal' round brilliant cut has changed through out history, but in 1972 Euliz calculated the proportions necessary for 100% brilliance in a diamond. We are currently translating the work from German and will provide more information on the solution in the near future.

Proportions %diameter Ideal Brilliant 1926 Parker Brilliant 1951 Tolkowsky Brilliant 1919 Practical Fine Cut 1939 Standard Brilliant 1969 Eulitz Calculated Brilliant 1972

Crown Height 19.2% 10.5% 16.2% 14.4% 14.6% 14.45%

Girdle Thickness - - - - - 1.5%

Pavilion Depth 40.0% 43.4% 43.1% 43.2% 43.1% 43.15%

Table Diameter 56.1% 55.9% 53.0% 56.0% 57.5% 56.5%

Crown Facets Angle (to girdle) 41.1 25.5 34.5 33.2 34.5 33.36

Pavilion Facets (to girdle) 38.7 40.9 40.75 40.8 40.75 40.48

Crown Height: Pavilion Depth 1:2.07 1:4.13 1:2.66 1:3 1:2.95 1:3

Light Yield 29.88% 42.39% 32.39% 33.03% - -

Brilliance Grade 98.4% Low 99.5% 99.95% 99.5% 100%

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Criteria	Unusual	Good	Very Good	Good	Unusual
Crown Angle	< 26.9	27.0 to 30.6	30.7 to 37.7	37.8 to 40.6	40.7 +
Pavilion Angle	< 38.4	38.5 to 39.5	39.6 to 42.2	42.3 to 43.1	43.2 +
Table width	71%+	70% to 67%	66% to 53%	52% to 51%	< 50%
Crown height	< 8.5%	9% to 10.5%	11% to 16%	16.5% to 18%	18.5% +
Girdle thickness	extremely thin	very thin	thin & medium	thick & V thick	extremely thick
Pavilion Depth (for pointed culet)	< 39.5%	40% to 41%	41.5% to 45%	45.5% to 46.5%	47%+
Culet Size			pointed to 1.9%	2% to 3.9%	4%+
Total depth	< 52.9%	53.0% to 55.4%	55.5% to 63.9%	64% to 66.9%	67.0%+

Proportions %diameter	Ideal Brilliant 1926	Parker Brilliant 1951	Tolkowsky Brilliant 1919	Practical Fine Cut 1939	Standard Brilliant 1969	Eulitz Calculated Brilliant 1972
Crown Height	19.2%	10.5%	16.2%	14.4%	14.6%	14.45%
Girdle Thickness	-	-	-	-	-	1.5%
Pavilion Depth	40.0%	43.4%	43.1%	43.2%	43.1%	43.15%
Table Diameter	56.1%	55.9%	53.0%	56.0%	57.5%	56.5%
Crown Facets Angle (to girdle)	41.1	25.5	34.5	33.2	34.5	33.36
Pavilion Facets (to girdle)	38.7	40.9	40.75	40.8	40.75	40.48
Crown Height: Pavilion Depth	1:2.07	1:4.13	1:2.66	1:3	1:2.95	1:3
Light Yield	29.88%	42.39%	32.39%	33.03%	-	-
Brilliance Grade	98.4%	Low	99.5%	99.95%	99.5%	100%