Diamond Symmetry – What Is It?
The symmetry of a diamond refers to the arrangement of the facets and finished angles, created by the diamond cutter. Excellent symmetry of a well-cut and well-proportioned diamond can have a great effect on the diamond’s beauty. Grading reports will often state the diamond’s symmetry in the following terms: Excellent, Very good, Good, Fair, or Poor.
It is often assumed that diamonds with poor symmetry were cut by professionals with poor skills. However just the opposite may be quite true.
When a rough diamond is being polished, the goal usually consists of creating the heaviest and most valuable diamond carat weight possible. An experienced cutter may be able to effectively perform this function by polishing a diamond with imperfect symmetry to avoid inclusions (negatively effecting the diamond clarity). It is also a fact that “key weights” (Like 1.0 carat or 2.0 carats) can be priced much higher than weights just a fraction below. (Like .99 carats or 1.99 carats)
The experienced diamond professional may decide to create a diamond with variations in the girdle thickness, an off-center table or culet, or a tilted table in order to achieve the “Key weight”.
The information above can be very confusing, but if you follow the chart below you’ll get a better understanding. To basically sum it all up; the more symmetrical the diamond is the more beautiful it’s diamond cut it. The more fire and ice, the more brilliance, the more sparkle. The better light passes through. When comparing GIA, or EGL, or any appraisal card check out the symmetry of the diamond and come back here and compare. It’ll make a world of difference!
The Diamond Symmetry Chart
Type: Round Brilliant Cut
| Diamond Cut Grade | Excellent | Very Good | Good | Fair – Poor |
| Difference in Value | 10 – 15% More | 5 – 10% More | 0% Even | 10 – 20% Less |
| Table % | 53 – 57 | 58 – 61 | 62 – 64 | 65+ |
| Depth % | 62.5 – 60.6 | 62.9 – 59.5 | 63.9 – 57 | 64+ or 56.9 & below |
| Polish | Excellent – Very Good | Very Good – Good | Good | Fair – Poor |
| Symmetry | Excellent – Very Good | Very Good – Good | Good | Fair – Poor |
| Culet | None – Very Small | Very Small – Small | Small – Medium | Medium – Large |
| Girdle | Thin – Medium | Thin – Thick | Very Thin – Thick | Extremely Thin – Very Thick |
Type: Square Cuts – Princess, Radiant, Emeralds
| Diamond Cut Grade | Excellent | Very Good | Good | Fair – Poor |
| Difference in Value | 10 – 15% More | 5 – 10% More | 0% Even | 10 – 20% Less |
| Table % | 65 – 70 | 71 – 75 | 76 – 80 | 85+ |
| Depth % | 66 – 71 | 71 – 75 | 76 – 80 | 80+ |
| Polish | Excellent – Very Good | Very Good – Good | Good | Fair – Poor |
| Symmetry | Excellent – Very Good | Very Good – Good | Good | Fair – Poor |
| Culet | None – Very Small | Very Small – Small | Small – Medium | Medium – Large |
| Girdle | Thin – Medium | Thin – Thick | Very Thin – Thick | Extremely Thin – Very Thick |
Type: Elongated Cuts – Radiants, Emeralds
| Diamond Cut Grade | Excellent | Very Good | Good | Fair – Poor |
| Difference in Value | 10 – 15% More | 5 – 10% More | 0% Even | 10 – 20% Less |
| Table % | 65 – 69 | 70 – 74 | 75 – 80 | 80+ |
| Depth % | 64 – 69 | 63 – 71 | 72 – 78 | 79+ |
| Polish | Excellent – Very Good | Very Good – Good | Good | Fair – Poor |
| Symmetry | Excellent – Very Good | Very Good – Good | Good | Fair – Poor |
| Girdle | Thin – Medium | Thin – Thick | Very Thin – Thick | Extremely Thin – Very Thick |
| Culet | None – Very Small | None – Small | Small – Medium | Medium – Large |
| Length / Width Ratio | 1:1.35 – 1:1.42 | 1:1.29 – 1:1.49 | 1:1.20 – 1:1.60 | Subjective |
Type: Pear
| Diamond Cut Grade | Excellent | Very Good | Good | Fair – Poor |
| Difference in Value | 10 – 15% More | 5 – 10% More | 0% Even | 10 – 20% Less |
| Table % | 55 – 58 | 53 – 61 | 50 – 64 | 48 – 69 |
| Depth % | 59 – 63 | 57 – 65 | 55 – 68 | 50 – 75 |
| Polish | Excellent – Very Good | Very Good – Good | Good | Fair – Poor |
| Symmetry | Excellent – Very Good | Very Good – Good | Good | Fair – Poor |
| Girdle | Thin – Medium | Thin – Thick | Very Thin – Thick | Extremely Thin – Very Thick |
| Culet | None – Very Small | None – Small | Small – Medium | Medium – Large |
| Length / Width Ratio | 1:1.45 – 1:1.60 | 1:1.35 – 1:1.70 | 1:1.25 – 1:1.80 | 1:1.20 – 1:2.0+ |
| Bow-Tie Effect | None – Minimal | Minimal – Average | Average – Significant | Significant |
Type: Marquise
| Diamond Cut Grade | Excellent | Very Good | Good | Fair – Poor |
| Difference in Value | 10 – 15% More | 5 – 10% More | 0% Even | 10 – 20% Less |
| Table % | 55 – 58 | 53 – 61 | 50 – 64 | 48 – 69 |
| Depth % | 59 – 63 | 57 – 65 | 55 – 68 | 50 – 75 |
| Polish | Excellent – Very Good | Very Good – Good | Good | Fair – Poor |
| Symmetry | Excellent – Very Good | Very Good – Good | Good | Fair – Poor |
| Girdle | Thin – Medium | Thin – Thick | Very Thin – Thick | Extremely Thin – Very Thick |
| Culet | None – Very Small | None – Small | Small – Medium | Medium – Large |
| Length / Width Ratio | 1:1.95 – 1:2.05 | 1:1.8 – 1:2.2 | 1:1.65 – 1:2.3 | 1:1.5 – 1:2.4 |
| Bow-Tie Effect | None – Minimal | Minimal – Average | Average – Significant | Significant |
Type: Oval
| Diamond Cut Grade | Excellent | Very Good | Good | Fair – Poor |
| Difference in Value | 10 – 15% More | 5 – 10% More | 0% Even | 10 – 20% Less |
| Table % | 55 – 58 | 53 – 61 | 50 – 64 | 48 – 69 |
| Depth % | 59 – 63 | 57 – 65 | 55 – 68 | 50 – 75 |
| Polish | Excellent – Very Good | Very Good – Good | Good | Fair – Poor |
| Symmetry | Excellent – Very Good | Very Good – Good | Good | Fair – Poor |
| Girdle | Thin – Medium | Thin – Thick | Very Thin – Thick | Extremely Thin – Very Thick |
| Culet | None – Very Small | None – Small | Small – Medium | Medium – Large |
| Length / Width Ratio | 1:1.35 – 1:1.42 | 1:3- 1:1.5 | 1:1.25 – 1:1.65 | 1:1.15 – 1:1.9 |
| Bow-Tie Effect | None – Minimal | Minimal – Average | Average – Significant | Significant |
Please be aware that all data represented in the tables above can vary slightly. These charts are to be used for reference only, and not for exact or legal purposes.