The Details That Perfect a Diamond
Polish and symmetry are two quality grades that appear on every diamond certificate alongside the 4Cs. While they receive less attention than cut, color, clarity, and carat, they play a meaningful role in how a diamond performs optically. Understanding these grades helps you make fully informed purchasing decisions.
What Is Polish
- Definition: Polish measures the smoothness of a diamond's facet surfaces as left by the cutting and polishing process
- What it affects: Surface smoothness determines how cleanly light enters and exits each facet. A poorly polished facet scatters light rather than reflecting it precisely
- Grades: Excellent, Very Good, Good, Fair, Poor
- What to look for: Polish lines, scratches, burns, rough surfaces — all visible under 10x magnification. These are manufacturing defects, not natural characteristics
What Is Symmetry
- Definition: Symmetry measures how precisely a diamond's facets are aligned, shaped, and positioned relative to each other
- What it affects: Symmetry determines the balance of light performance across the diamond. Asymmetric facets create uneven sparkle patterns
- Grades: Excellent, Very Good, Good, Fair, Poor
- What to look for: Misaligned facets, off-center table, uneven crown heights, misshapen facets
How Much Do They Matter
- Excellent: The gold standard. Optimal light performance with no detectable defects under magnification
- Very Good: Minor deviations visible only under magnification. No impact on face-up beauty. Excellent value choice
- Good: Noticeable deviations under magnification that may slightly affect light performance. Acceptable for budget-conscious buyers but not ideal
- Fair/Poor: Visible impact on light performance. Avoid for engagement rings and fine jewelry
Recommendations
- For engagement rings: Excellent or Very Good for both polish and symmetry. These are easily achievable with lab-grown diamonds and the price premium is minimal
- For accent stones: Very Good is perfectly sufficient. At small sizes, polish and symmetry differences are invisible
- Budget priority: If you must choose, prioritize symmetry over polish. Symmetry has a more direct impact on light performance
- Triple Excellent: A diamond with Excellent cut, Excellent polish, and Excellent symmetry is called 'triple excellent' — the highest quality designation
