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.

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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.


Selecting a Polish Grade

Of the recorded attributes on the GIA report, the Polish grade has the least impact on the diamond’s price and value. With updates in technology, a larger percentage of diamonds earn a Very Good or Excellent Polish grade, especially in round cut diamonds. Therefore, if you find a diamond with a Very Good cut grade and that is part of the reason for a good value, it may be well worth your while.


Polish Examples

Polish Lines: small grooves located on facets resulting from diamond polishing. You can tell they are difference from surface graining because they do not cross facet junctions. Only when extreme, they can affect a diamond’s sparkle.

Abrasion: small nicks and cuts along the junctions where facets meet. Typically a result of wear and tear.

Extra Facet: During manufacturing, an extra facet is manufactured on a diamond, typically in order to remove an inclusion.

Lizard Skin: A bumpy looking surface on the facet that almost looks like natural rough diamond skin.

Nick: A small notch on a diamond’s surface that doesn’t appear to have depth. It can be like a very minute chip.

Pit: A tiny white dot on the surface of skin that resembles a pinpoint.

Natural: A portion of rough diamond skin that remains on a surface during the manufacturing process. Typically, it occurs near the diamond’s girdle.

Burn Mark: A whitening of the diamond surface resulting from excess heat applied during the polishing process. It is very difficult to reverse a burn mark on a diamond.

Rough Girdle: rough skin patches on the girdle that cannot be polished away easily.

Scratch: A small line on the surface of the diamond that doesn’t appear to have depth. It is very difficult to scratch a diamond. A scratch can be repolished away.

lines remaining on the surface from improper diamond polishing an abrasion from polishing on the diamond facet an extra facet above the regular amount probably excluding an inclusion lizard like skin on the diamond's surface a scratch like nick on the diamond's facet a small pit or cavaity shown on the surface of the diamond natural skin from the rough diamond remaining on the skin surface a burn mark from improper polishing on a hot diamond wheel a rough girdle most likely from unpolished rough diamond a scratch on the surface of a facet