Marcel Tolkowsky "Ideal" Brilliant Cut - 1914
Though there was no single inventor of the round brilliant cut diamond shape, it has often been credited to a
seventeenth century Venetian cutter named Vincenzio Peruzzi, but it wasn't until the introduction of the Tolkowsky Brilliant almost 100 years ago that a standardised formula for proportions was introduced.
Since then the 'Tolkowsky Brilliant' has been the blueprint for all modern round cuts. It is believed that even though
Marcel made some slight errors in his calculation, his set of proportions achieve what is known as 'Total Internal
Reflection' or 'Zero leakage', simply meaning that all light which enters the stone is returned back through the crown
to the observer.
Upon exiting the diamond the light splits into the spectrum of colour (known as dispersion). This is how a
diamond achieves its 'Fire'. Any light which bounces off the stone (known as reflection) gives 'brilliance'.
The combination of the two is known as 'scintillation'.
Stones cut with the Tolkowsky proportions are believed to have the best or "Ideal"* combination of both. Obviously as the stone moves away from these optimum proportions its ability to return light is affected.
As the round brilliant cut evolved over the years many versions of the 'Ideal' have been developed and introduced, but on the whole they don't deviate greatly from the original.
As it would be impossible for every stone to be cut to meet 'Ideal' proportions, Certification houses allow tolerances within a range of measurements to be included within the same grade.
*Some grading houses dislike the term ideal and won't use it, while others use it a little too generously.
A large or spread table on a diamond may indicate a poorly cut stone and it could lack the brilliance and fire of a well-proportioned diamond. Nevertheless they can appear larger to the naked eye than the stone weight would indicate.
Polish and Symmetry
Do not confuse these grades as an indication of the quality of the diamond's Make/cut. Consider the polish, as you would a dirty window! A diamond with a poor polish will not allow light to pass into and out of itself as easily as a stone with an excellent polish. Also a diamond may have excellent symmetry but could still have poor angles and proportions.
Hearts and Arrows
Hearts and Arrows denote a stone with perfect faceting, both in size and alignment. The facets on the top of the stone
(crown) align perfectly with the corresponding bottom (pavilion) facets. Simply put, the top is exactly above the bottom
and when viewed through a special scope the stone will display the Hearts and Arrows pattern.
This perfect alignment of faceting produces the maximum reflection between the crown and pavilion facets. Though generally seen as an
indication of a 'better than average make' it however is not necessarily an indication of a superior cut, as the
stone's angles and proportions may still be those of a lower grade.
Always check for fluorescence on a diamond. A stone with medium to strong fluorescence may appear milky and thus should
be priced slightly lower than the same stone with a 'none' or 'faint' reading.
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