Polish and symmetry are graded separately from overall cut grade on most certificates, but they get comparatively little attention from buyers focused on the headline 4Cs. Both measure execution quality in ways that affect how a stone actually performs visually — and both are, like cut grade, entirely a function of the cutter's skill rather than the original rough.
What polish grade measures
Polish grade assesses the smoothness of a diamond's facet surfaces — microscopic scratches, pits, or burn marks left from the cutting and polishing process reduce the grade. Poor polish can subtly reduce brilliance by scattering light at the surface rather than allowing it to pass cleanly through the stone.
What symmetry grade measures
Symmetry evaluates how precisely a stone's facets align — misshapen facets, off-center culets, or uneven proportions between mirrored sections of the stone. Poor symmetry can create visible optical inconsistencies, sometimes described as "dead spots" where light doesn't return evenly across the stone's face.
Why these matter more at scale than buyers assume
For a single stone, minor polish or symmetry deviations are often not visible without magnification. But for buyers sourcing parcels intended for matched-set jewelry — pavé settings, eternity bands, or matched pairs — consistency in polish and symmetry across the parcel matters more than any individual stone's grade, since visual mismatches within a single piece are far more noticeable than in an isolated stone.
What to check during evaluation
Beyond reading the certificate field, physically examine a sample of stones under magnification specifically for surface quality and facet alignment — not just clarity inclusions. This is part of the broader inspection process covered in our guide on what happens during a diamond quality inspection.
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Published by the VisitSDB team. Updated .
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