The cut of a diamond significantly impacts its appearance in three main ways: its brilliance (the brightness resulting from reflected and refracted light), fire (the dispersion of light into vivid color flashes), and scintillation (the sparkling flashes of light and dark when the diamond or light source is moved).
Depth and Table Percentage
The cut of a diamond is determined by two key factors: its depth and table percentage. As the largest facet, the diamond table significantly contributes to the gemstone’s renowned sparkle. But what exactly is a diamond table?
The diamond’s table is the flat facet visible when viewing the stone from above. Its primary function is to refract incoming light rays and allow reflected light rays from within the diamond to reach the observer’s eye. A perfectly cut table will bestow the diamond with breathtaking fire and brilliance.
Calculating Depth Percentage
In a diamond grading report, the table percentage is determined by dividing the table diameter by the average girdle diameter. For diamonds with unique shapes, the table percentage is calculated by dividing the table width by the diamond’s widest section. Essentially, the table percentage represents the size ratio of the diamond’s top facet to its total width.
The ideal table and depth percentages vary according to the diamond’s shape, and a one-size-fits-all approach does not apply. The percentages must work harmoniously to refract and direct light through the diamond’s facets efficiently and to emit light through the table to the observer’s eyes. A larger table may restrict the upper facets’ ability to disperse light, while a smaller table might reduce light entry, affecting the diamond’s overall brilliance.
Diamond Proportions & Cut
Diamond cut involves the consideration of a diamond’s proportions—the relationship between the size, shape, and angle of each facet. Various combinations are possible, giving rise to unique ideal depth and table percentages for each diamond shape. Below are the ideal table and depth percentages for different diamond shapes:
Diamond Depth and Table
| Shape | Ideal Table % | Depth % |
|---|---|---|
| Round | 53-58 | 59-62.3 |
| Princess | 67-72 | 64-75 |
| Oval | 53-63 | 58-62 |
| Emerald | 61-69 | 61-67 |
| Asscher | 61-69 | 61-67 |
| Marquise | 53-63 | 58-62 |
| Pear | 53-63 | 58-62 |
| Heart | 53-63 | 58-62 |
| Radiant | 61-69 | 61-67 |
| Cushion | 61-67 | 61-67 |
Significance of Table and Depth Percentage
Understanding the ideal table and depth percentages of a diamond shows how well-proportioned diamonds result in superior cut grades.
The table and depth percentages are significant factors in determining a diamond’s overall cut grade. Of the 4 C’s of a diamond, the cut is the most intricate and challenging to analyze. To grade a diamond’s cut, labs calculate the proportions of its facets, assessing how effectively the diamond interacts with light to produce brightness, fire, and scintillation, all elements of its brilliance. Additionally, a diamond’s cut grade evaluates the design and artistic quality of the gemstone, including its weight relative to diameter, girdle thickness, facet symmetry, and polish quality.
GIA, EGL Diamond Cut Classifications
The diamond’s cut grade is determined on a grading scale, which varies depending on the laboratory. The Gemological Institute of America (GIA) and European Gemological Laboratory (EGL) use a scale ranging from Excellent to Poor, while the American Gem Society employs a numerical scale from zero to ten.
Though size or carat weight might initially seem more important, the cut, which includes the diamond table percentage, is substantially more complex. Given the diamond table’s crucial role in influencing its overall quality, it is essential to research the ideal table percentage for the diamond you desire.
