Polish is the grade for the smoothness of the facet surfaces, from Excellent to Poor. The grader looks at 10x for pits, nicks, polish lines, scratches, burn marks and rough patches.
In more detail
On a GIA round, polish limits the cut grade. Excellent or Very Good polish allows Excellent, Good allows at most Very Good, Fair allows Good, and Poor gives Poor. Polish doesn't say where the facets point, so it can't predict a bow-tie.
On a grading report
In the additional grading section of GIA and IGI reports. IGI gives a polish grade for every shape and color.
Related terms
- Symmetry: Symmetry is the report grade, from Excellent to Poor, for the exactness of a stone's outline. It also covers the shape, placement and alignment of the facets.
- Cut grade: The cut grade rates how well a diamond's proportions and finish work, from Excellent to Poor. GIA gives it only to standard round brilliants in the D-to-Z color range.
- Polish lines: Polish lines are fine parallel grooves and ridges left by polishing. They can occur on any facet but don't cross facet junctions, and they look transparent or white.
- Burn mark: A burn mark is a hazy area on a facet surface, caused by too much heat during polishing. It is also called a burned facet.
- Triple Excellent: Triple Excellent is trade shorthand for a GIA round brilliant with Excellent cut, Excellent polish and Excellent symmetry.