While they both would seem related to a diamond’s cut grade, for they both play critical roles in determining the overall quality of the finish, polish and symmetry appear as separate items on a diamond grading report.
Polish relates to the degree to which the surface is a of the stone is smooth and glass-like. In essence, a high-quality polish suggests the almost or complete absence of surface imperfections.
Symmetry relates to the precision to which the facets have been arranged. Gemologists grading the stone will consider their sizes and shapes, the alignment of the crown and pavilion, the girdle width, and the position of the culet relative to the table.
Both polish and symmetry are rated on a scale ranging from Excellent to Poor.
Imperfections that will reduce the assessment given for polished include the following:
Abrasion: Scratches or pits along a facet edge that result in a fuzzy line instead of a sharp junction.
Burn: A whitish haze caused by excessive heat during the polishing process.
Laser Manufacturing Remnant: A remnant of laser manufacturing that typically appears as a transparent or white groove.
Lizard Skin: An uneven texture on a facet caused by polishing it against the grain.
Nick: A small notch on a facets junction.
Pit: A small hole in the surface that appears as white dot.
Rough Girdle: A girdle that is marked with nicks and pits.
Scratch: A white line in the surface of the stone that is curved or straight.
Polish Lines: Parallel lines that remain after polishing.