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CUT
The main diamond cuts are:
| Round Brilliant |
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Emerald Cut |
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Princess Cut |
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Heart Cut |
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| Oval Cut |
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Marquise Cut |
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Pear Cut |
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Round Brilliant |
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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
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PAVILION
Lower
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8 Pavilion
16 Lower Girdle
1 Culet
Total facets: 25 Pavilion Facets
Thus there are 58 facets in total.
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Girdle:
 This is the waist band in the middle, and is sometimes faceted. |
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)
| 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
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 certificated loose diamond, so every certificated 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.
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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 |
- |
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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% |
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| Brilliance Grade |
98.4% |
Low |
99.5% |
99.95% |
99.5% |
100% |
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