The Diamond Polish – Is it Important?

Polishing a diamond on a polishing wheel

Polishing a diamond on a polishing wheel

The diamond polish refers to the quality of a diamond’s surface condition which is a result of the polishing process. However, the polish of a diamond can also be affected by flaws created after the cutting process. Such blemishes are usually referred to as “wear and tear”.

Thus, a diamond’s polish features are located on the surface of a diamond. Flaws inside the diamond on the other hand are graded within the “clarity” category of the 4Cs as inclusions.

A diamond with an “Excellent/Ideal” Polish grade has a very smooth surface that lets the light in and out in the most efficient manner. This way a diamond’s luster is maxed out providing the highest amount of brilliance, fire and scintillation. A diamond with a poorer Polish grade however, can affect a diamond’s light permeability and thus the overall luster of a diamond negatively.

Which polish grade to choose?

As you know, I am a strong advocate of not compromising on the diamond cut. I think that if your budget allows for it, you should always go for an “Excellent/Ideal” cut grade. GIA only gives an “Excellent” cut grade to diamonds that have at least an “Excellent” or “Very Good” polish grade.

Now, this might make you think that you should necessarily choose a diamond with an “Excellent” or “Very Good” polish grade. And in fact this is the safest solution. In my own experience of working 2 years in a brick and mortar jewellery store however, I could only distinguish “Excellent” and “Good” polish grades with difficulty and a 10x loupe. In my opinion polish flaws of a diamond with a “Good” polish grade can only rarely be made out with the naked eye.

Thus, there might be diamonds which receive an only “Very Good” cut grade due to the “Good” polish grade. In such a case in which the diamond’s cut grade is only downgraded because of a “Good” polish grade, it would usually still be advisable to go for this stone. Most customers are no diamond experts and might not know the specific reasons for which a diamond does not receive the best cut grade.

You can always contact me and I will be more than happy to help you out!

Which factors influence the polish grade?

Polish flawsThe polish quality of a diamond is directly influenced by the polishing process. A better polish grade is achieved by polishing for a longer time and by using a better polishing wheel with diamond dust consisting of particularly fine grain.

The following list contains the most common polish flaws. If you want to know exactly how single polish flaws can affect the polish grade in GIA grading system please click here.

What I would finally like to add is the following: A diamond’s symmetry and polish grades do affect the overall cut grade of a diamond. But the cut itself is more important than the symmetry and especially the polish of a diamond (unless you choose a fair or even poor polish grade). The reason is simply that only an “Excellent” cut grade makes sure that the crown and pavilion angles and the other proportions of a diamond are best suited for refracting the light in the most brilliant way. In great part it is the exact angles and proportions of a diamond that determine the light performance of a diamond.

Thus, if you are faced with having to make a choice between a better symmetry/polish grade or better cut proportions I would strongly advise to go for the better cut proportions.

Many people want to have an “Excellent” grade in cut, symmetry and polish and this is fine. You can usually get a better bang for the buck though, if you choose a “Very Good” symmetry and polish grade. I guarantee that in such a case you will never be able to tell any difference with the naked eye.


Read Next: Carat Weight