Diamond Symmetry
How facet alignment controls the path of light through your diamond.
Diamond symmetry refers to how precisely the facets of a diamond align and intersect. When facets are perfectly symmetrical, light enters the stone, bounces between the pavilion facets, and exits through the crown in an even, balanced pattern of brilliance and fire. Any misalignment — even by fractions of a degree — can redirect light away from the viewer's eye.
Symmetry is evaluated under 10x magnification and graded on a five-point scale by the GIA. It is one of the three components (along with polish and proportions) that contribute to the overall cut grade for round brilliant diamonds.
Common Symmetry Deviations
When grading symmetry, gemologists look for specific deviations from perfect alignment:
- Off-center table — The table facet is not centered on the crown, causing uneven light distribution.
- Off-center culet — The culet point is shifted from the center of the pavilion, disrupting the internal light path.
- Misaligned facets — Crown and pavilion facets don't meet precisely at the girdle, creating uneven reflections.
- Wavy girdle — The girdle undulates rather than forming a uniform plane, creating thickness variations.
- Table/culet not parallel — The flat table and the culet are not in parallel planes, tilting the optical axis.
- Extra or missing facets — The diamond has more or fewer facets than the standard for its shape (57 or 58 for round brilliant).
- Naturals — Parts of the original rough crystal surface remain on the polished stone.
Symmetry Grades
| Grade | What It Means | Impact on Light Performance |
|---|
| Excellent (EX) | No symmetry defects visible under 10x magnification. Facets are precisely aligned, creating perfectly balanced light return. | Maximum brilliance and fire. The benchmark for premium diamonds. |
| Very Good (VG) | Any defects are very difficult to see under 10x magnification. Extremely minor deviations that don't affect visual appearance. | Virtually indistinguishable from Excellent in real-world viewing conditions. |
| Good (G) | Defects are difficult to see under 10x magnification but may include slightly misaligned facets or a marginally off-center table. | Negligible impact on appearance. A strong value choice for budget-conscious buyers. |
| Fair (F) | Defects are noticeable at 10x magnification and may be visible to the unaided eye. Light performance is measurably reduced. | Some loss of brilliance. Consider upgrading if your budget permits. |
| Poor (P) | Defects are visible to the unaided eye. Significant facet misalignment creates dark zones, uneven sparkle, and dull areas. | Noticeably diminished brilliance and fire. Not recommended. |
How Symmetry Affects Value
Symmetry grade has a meaningful impact on price. A diamond with Excellent symmetry and Excellent polish (known as a "triple excellent" when paired with an Excellent cut grade) commands a premium of 10–15% over a diamond with Good symmetry and Good polish, all other factors being equal.
For engagement rings and diamond necklaces where the diamond is the centerpiece, we recommend Very Good or Excellent symmetry. For side stones or accent diamonds in tennis bracelets, Good symmetry is typically more than adequate.
Our Recommendation
Excellent and Very Good symmetry are nearly identical to the naked eye. Unless you are purchasing an investment-grade diamond, Very Good symmetry offers the best balance of beauty and value. Avoid Fair and Poor symmetry, as the impact on light performance is visible and measurable.
Shop Certified Diamonds
Browse thousands of GIA, IGI, and HRD certified diamonds with 360° video.