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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.
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
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
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 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.
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.
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.
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.
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.