Diamond Cut, Brilliant ideal, Pavilion & Crown facets..
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CUT

The main diamond cuts are:

Round Brilliant Round Brilliant Diamond Emerald Cut Emerald Cut Diamond Princess Cut Princess Cut Diamond Heart Cut Heart Cut Diamond
Oval Cut Oval Cut Diamond Marquise Cut Marquise Cut Diamond Pear Cut Pear Cut Diamond Round Brilliant Round Brilliant Diamond

Popular diamond cuts include Heart, Emerald, Marquise (Oval with pointed ends), Oval, Pear, and Princess. There are unusual cuts appearing all the time such as the J C Millennium (89 facets) which is basically a Round Cut stone similar to the Round Brilliant, and the Radiant Cut which is an octagonal stone similar to an Emerald or Step Cut. If you would like more detailed information on any particular cut just e-mail customer services.E-mail: Help

Cut:
The most popular cut is the modern round brilliant (R/B):
Every loose R/B diamond purchased from us has passed the DCA quality test.

Round Brilliant Facets

The standard brilliant comprises:

CROWN
Upper:

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

Total facets: 33 Crown Facets

facets on a round brilliant cut diamondRound Brilliant Diamond top view
 

PAVILION
Lower :

8 Pavilion
16 Lower Girdle
1 Culet

Total facets: 25 Pavilion Facets

Thus there are 58 facets in total.

 

Round Brilliant Diamond side viewfacets on a round brilliant cut diamond

Girdle:

This is the waist band in the middle, and is sometimes faceted. Girdle with GIA inscription Girdle with GIA inscription

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)

CriteriaUnusualGoodVery GoodGoodUnusual
Crown Angle< 26.927.0 to 30.630.7 to 37.737.8 to 40.640.7 +
Pavilion Angle< 38.438.5 to 39.539.6 to 42.242.3 to 43.143.2 +
Table width71%+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 thicknessextremely thinvery thinthin & mediumthick & V thickextremely 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

A ratio can be determined for any given brilliant cut diamond, which when calculated, will yield its deviation from the 100% brilliance of a mathematically perfect cut. Diamond Cut Analysis (DCA) We calculate this before we purchase a diamond, so every diamond we sell has passed the DCA quality cut test. Generally we reject stones that fall below 5% deviation in any criteria, which is approx 9 out of every 10 diamonds. You might think this is harsh, but we always aim to 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.
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%