Polish Grade Guide

Diamond polish grade explained. Excellent vs Very Good vs Good: how surface finish affects brilliance, plus live market premiums at every grade.

The premium for Excellent polish over Very Good is tiny, usually a few percent, because most cutters produce Very Good or better as a minimum standard. GIA grades the vast majority of modern stones as Excellent or Very Good on polish, and the price difference between the top two grades on a GIA report is small enough that Excellent is almost always worth the upgrade. Where polish matters most is at the lower end: a Good polish grade suggests the cutter compromised on the final finishing, which often correlates with a less carefully cut stone overall.

Always insist on Very Good or better polish. Excellent is cheap at the top, so pay the small premium. Skip Good or Fair polish outright; the saving is trivial and the reduced brilliance is not worth it.