| In 1919, a Belgian mathematician, Marcel | | | | proportions make. When a diamond has been cut |
| Tolkowsky, who came from a family of diamond | | | | in such a way that all proportions are correct, the |
| cutters, published a Masters thesis on the best | | | | diamond will reflect all of the light that enters the |
| proportions for round brilliant diamonds. This work | | | | diamond, irrespective of the direction that the light |
| formed the basis of the defining proportions for | | | | has come from. All this light is then reflected out |
| what are now known as "Ideal cut diamonds". It | | | | through the top of the diamond, leading to the |
| must be noted however that different grading | | | | brilliant flashes of light and rainbow colours that we |
| laboratories allocate different names to the basic | | | | associate with diamonds. |
| Ideal cut diamond. American Ideal Cut, Superb | | | | Sometimes, a diamond cutter will sacrifice the |
| Ideal Cut or even Excellent Cut all refer to | | | | proportions of a diamond to fit the diamond into a |
| diamonds that match the range of acceptable | | | | specific size (carat) category, allowing for the |
| geometric proportions based on Tolkowsky's | | | | potential of a higher price. If the diamond has |
| work. | | | | been cut too deep, the diamond will appear black |
| So, what are these proportions? The diameter of | | | | in the centre. If the diamond has been cut too |
| the diamond is considered to be 100%, so all | | | | shallow, the diamond will look dull and lifeless. |
| percentages quoted are relative to the diameter | | | | When buying a round brilliant diamond, make sure |
| (or 100%) of the diamond. | | | | that the accompanying diamond certificate |
| - Table diameter = 52.4 - 57.5% | | | | contains a printed insert providing the full details of |
| - Crown angle = 33.7º - 35.8º | | | | the proportions of your diamond. This is the best |
| - Girdle thickness = 0.51 - 2.95% | | | | way to ensure that the diamond you have |
| - Pavilion depth = 42.2 -43.8% | | | | purchased has been cut to acceptable, ideal |
| - Total depth = 58.7 - 62.3% | | | | proportions. |
| You may be asking what difference these | | | | |