IGI, GIA and HRD are the most reliable certificates.
Polish
Polish
Describes the quality of finish on the outer surface of the diamond. A high grade maximises light reflection and brilliance.
Excellent (EX) — Perfectly smooth surface: maximum brilliance.
Very Good (VG) — Very good polish, with minor features visible only under a 10x loupe.
Good (G) — Small polishing marks visible under 10x, invisible to the naked eye.
Symmetry
Symmetry
Evaluates how precisely the facets align and intersect. Minor asymmetries can affect light travel and brilliance. Excellent and Very Good are recommended.
Excellent — Perfect alignment of all facets.
Very Good — Very slight asymmetries, visible only under 10x magnification.
Good — Minor asymmetries visible under 10x loupe, not to the naked eye.
Fair / Poor — Noticeable asymmetries visible to the naked eye: not recommended.
