Round Brilliant Cut Diamond
The term Brilliant is today so closely associated with the mineral diamond that people often speak of "brilliant" when they actually mean the mineral diamond. The description "brilliant" is used only when the diamond is genuine. Of all the different cut forms, the brilliant is the classic. Its designation applies exclusively to the circular form of cut which exhibits at least 32 facets and a table on the crown and at least 24 facets and a culet on the pavilion.
Facet Arrangement Of A Round Brilliant Diamond:
A round brilliant cut diamond has 58 facets, the largest being the table facet. The three sections of the round brilliant cut are: crown, girdle and the pavilion.
The crown consists of 33 facets: 8 star facets, 8 bezel facets and 16 upper girdle facets.
The crown and pavilion are joined together by the girdle. The girdle can be polished, faceted or frosted.
Depending on whether the culet is faceted, the pavilion has 24 or 25 facets: 8 pavilion main facets and 16 lower girdle facets.
Types of Brilliant Cuts:Until the start of the twentieth century, the forms of diamond cuts developed empirically as men strove to attain an optimum brilliance effect. It is only since around 1910 that theoretical calculations have been used that take into consideration light refraction, dispersion and hardness in order to achieve maximum brilliance through suitable proportions and symmetry ratios.
Tolkowsky Brilliant (1919 - Tolkowsky): This cut is regarded in America as the "standard" and is the basis for cut grading. Its brilliance meets the highest requirements.
Ideal Brilliant (1926 - Johnson and Roesch): The measurments of this cut take into consideration only light falling perpendicularly on the stone. On the other hand, no account is taken of light entering obliquely. Therefore, no great brilliance can be expected from this type of cut.
Practical Fine Cut (1939 - Eppler): This form of cut originated from practice, was therefore designated the "Practical Fine Cut". Its measurments were calculated so that even light entering obliquely was taken into account. The Practical Fine Cut departs considerably from the Ideal brilliant, but only slightly from the Tolkowsky cut. The Practical Fine Cut is the preferred type of brilliant in Germany.
Parker Brilliant (1951 - Parker): This cut form is only mentioned for the sake of completeness. It is not of great importance in relation to the brilliance effect, as the crown is too shallow.
Scandinavian Standard Brilliant (1969 - Tillander): Its values also originate in practice. Tillander based his calculations on a great many brilliants found on the market whose brilliance effect seemed outstanding to him.
Eulitz Brilliant (1972 - Eulitz): W.R Eulitz's work "Determining mathematically the optimum brilliance of brilliants" was published. Mr Eulitz showed mathematically that using certain proportions, a maximum light yield resulting from internal total reflection and an optimal color scattering can be attained. These mathematical values are very close to those determined by Eppler for the Practical Fine Cut.