Polish refers to the quality of the surface finishing of each cut surface, known as a facet, which should be as smooth and transparent as possible. This feature is usually graded in terms of Ideal (AGS), Excellent, Very Good, Good, Fair, and Poor. Polish is combined with the overall cut grade and other factors such as symmetry, depth and table percentages, and girdle and culet sizes to affect value.
A diamond with an Ideal or Excellent polish notation might have just a few hard-to-find polish lines left from the cutter's polishing wheel and are impossible to find with the unaided eye.
A diamond with a Very Good or Good notation may have just a few insignificant blemishes on the facet surfaces or transparent polish lines on a few facets that can't be seen with the unaided eye.
Fair or Poor
A diamond with a Fair or Poor notation may have more obvious polish lines or marks that can be seen with the unaided eye.