Diamond Polish

The diamond’s finish consists of 2 important attributes: Polish & Symmetry. A diamond’s Polish is determined by the manufacturing process of a diamond. Typically, after the diamond is cut and faceted, it is polished to bring out the shine and smooth finish of the diamond. Polish can affect the diamond’s sparkle if not done well. It is a secondary characteristic of the diamond’s cut grade that will sometimes, not always impact the assigned cut grade. Below, you’ll find the Polish scale and examples of blemishes that contribute to the Polish grade.

Polish Grade

a diamond polishing wheel with other tools to hold and facet the diamond used by manufacturers

GIA has established a diamond Polish scale, very similar to the Symmetry scale. The grades are based on the visibility of polish lines or other blemishes on the skin or surfaces of the diamond. The diamond is examined by gemologists at 10x magnification when determining the Polish grade.

Excellent: There are not visibility of polish lines or other blemishes at 10x magnification. Light is able to perfectly enter and exit the diamond, without affecting diamond sparkle or brilliance.

Very Good: There are minor polish details visible at 10x magnification. These polish lines or blemishes may have little or no impact on the diamond’s sparkle. The diamond can still earn an Excellent cut grade.

Good: There are some visible polish lines or blemishes, most likely only at 10x magnification. The diamond’s sparkle may be affected because light is not perfectly able to penetrate the diamond. The diamond can earn at most a Very Good cut grade.

Fair & Poor: There are noticeable finishing errors in the form of polish lines or blemishes. These blemishes have an impact on light performance and reduce the diamond’s ability to sparkle. The diamond can earn, at most, a Good cut grade.


What does polish mean on a diamond?

A very important factor in determining the brilliance of a diamond, polish refers to the smoothness of each facet of a diamond which in turn will determine how well light passes through it.

How are diamonds polished when being cut?

Diamonds are polished by a polishing wheel where the facets of the cut diamond are polished so that it reflects the light in the best possible manner. Polishing is important as it determines the level of fire and brilliance that the diamond will have.

How important is the polish grade?

The polish grade is extremely important as it can truly affect the diamond’s sparkle if not done correctly. It is a scale established by the GIA based on the visibility of polish lines and blemishes that are visible under 10x magnification.

Do lab diamonds have the same polish grades?

Yes, lab diamonds do have the same polish grades as their mined counterparts since lab diamonds have the same physical, optical and chemical properties as natural diamonds. The only difference lies in their origin. The rest of the process remains the same.

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