Diamond Basics
Polish and Symmetry: The Overlooked Grades
Polish and symmetry sit alongside the cut grade on a diamond report and independently affect how clean and crisp a diamond's light return appears.
What polish measures
Polish describes the smoothness of each facet's surface. Poor polish can leave microscopic lines, nicks or a hazy finish that slightly dulls brilliance, even on an otherwise well-proportioned stone.
What symmetry measures
Symmetry assesses how precisely facets align and meet — including whether the table is centred, facets meet at sharp points, and the outline is even. Poor symmetry can misdirect light and reduce sparkle.
How they combine with cut
For round brilliants, GIA factors polish and symmetry into the overall cut grade. For fancy shapes without an overall cut grade, polish and symmetry become even more important independent indicators of quality.
Buyer checklist
- ✓ Look for Excellent or Very Good polish and symmetry when possible
- ✓ Remember fancy shapes rely on these grades more heavily
- ✓ Ask for close-up photos or video if grades are Good or below
Verification tools & references
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