How important is Polish and Symmetry in a Diamond Certificate?

How important is Polish and Symmetry in a Diamond Certificate.

This question is one that arises in my business several times every week. The typical request comes in for a “Triple Excellent” of for “EX/EX/EX” diamond.

To begin with, one must understand that “Triple Excellent” applies only to Round Brilliant diamonds. GIA diamond grading reports do not grade “Cut” for Fancy Shape diamonds. A fancy shape diamond is anything other than a Round Brilliant Cut. This includes Cushion Cut, Princess Cut, Radiant Cut, Emerald Cut, Oval, Pear Shape or Marquise. This being the case, only a round diamond can be an Excellent Cut or EX/EX/EX or “Ideal Cut”.

With regard to Polish and Symmetry grading, GIA assigns a grade to each that can range from Excellent to Poor. There are five possibilities. They are Excellent, Very Good, Good, Fair and Poor.

It is my opinion that Polish and Symmetry are more important on a Round Brilliant diamond than on a fancy shape diamond. To many retail diamond buyers, this may seem somewhat surprising since there is no “Cut” grade assigned for fancy shapes and, therefore, Polish and Symmetry is all they have to go on when determining the “cut” of a particular fancy shape diamond.

Truth be told – a fancy shape diamond is all about the cut. Unfortunately, the determination of the beauty or brilliance of a fancy shape diamond has nothing at all to do with Polish and/or Symmetry! (For more on this, see below.)

With regard to Polish and Symmetry, whether it be a round or a fancy shape diamond, one must understand what these things really are. Polish refers to the appearance or lack thereof of any surface remnants or surface blemishes that remain on the diamond after the cutting is completed. These are not flaws or imperfections in the diamond. Think of the final diamond polishing process as being akin to sandpaper on wood. In a perfect situation, , there is no trace that the wood has been sanded as it is left in a pristine, smooth condition. This is also true with regard to diamond polishing.

Symmetry on the other hand is something specific to a diamond. This refers to the faceting of the diamond. Specifically, a diamond is cut with many different facets. In a round diamond there are 58 facets – or individual “planes” on the surface of the diamond. The number of facets on a fancy shape diamond varies. Symmetry refers to how precisely the “point” of each “facet” is aligned with the “point” of the adjacent “facet”.

One must realize that with regard to polish and/or symmetry, there are many facets and “points” of a diamond. Usually, the polish or symmetry grade of a particular diamond can be based on an extremely minute detail of just one or two facets.

In order to put this whole thing into perspective, one must understand that within the grades of Excellent and Very Good (and, in most cases of “Good”), the differences in these Polish and Symmetry grades are very minimal and have virtually no effect on the overall brilliance or sparkle of a diamond. We are talking about things that are apparent only under magnification and, even then, are extremely difficult to visualize.

“Fair” or “Poor” grades in either Polish and/or Symmetry are somewhat significant issues that may affect the overall beauty of the diamond. In these instances there are numerous misaligned facets or facets that are “way out of whack”. In the case of fair or poor “Polish”, there are numerous or somewhat more obvious surface blemishes that remain on the diamond’s surface. These diamonds should be avoided.

On the other hand, It must be understood that the differences between “Excellent”, “Very Good” and sometimes “Good” are very minor differences and are inconsequential to the overall appearance of a diamond. These are facet junction issues or surface issues that I assure you will never ever be aware of – even under magnification.

My advice is to stick with “Excellent” and/or “Very Good” in both Polish and Symmetry. More importantly, do not think that a diamond with “Excellent” Polish and/or Symmetry is any more beautiful that one that is “Very Good”.

Think of the difference in this way. Assume you have beautiful custom wood cabinets built in your home. Assume that these cabinets are made of beautiful wood and the craftsmanship of the project is spectacular. Assume the final step on the installation is applying the final coat of varnish to the the surface on which several coats of varnish has already been applied. If you then went over the entire surface of the many linear feet of cabinetry inside and out with a magnifying glass and found an exceptionally minuscule spec or blemish in the varnish on the inside of one cabinet, this would be the difference between “Excellent” or “Very Good”. Remember – this is with magnification and even so we are talking about something that is exceptionally minute!!

As in everything in life, we all want perfection in every way. But, as a diamond merchant for 40+ years, I assure you that I cannot tell the difference between “Very Good” and “Excellent” when it comes to Polish and/or Symmetry. I am human and do not possess the vision and technical analysis of a computer that is programmed to do nothing else except examine a diamond and every one of it’s facets under extreme magnification. I have no doubt that you also will never see any difference between “Excellent” and “Very Good” when it comes to Polish and Symmetry.

Retail diamond consumers often drive themselves “crazy” with details about somewhat trivial things. Today, advances in technology have taken the diamond cutting process and the ways in which diamonds are evaluated far beyond levels that were possible in the past. Realistically, we have gone way beyond the things that really matter – the overall beauty of a diamond!



I happen to think that many fancy shape diamonds are ugly. I also think that there are fancy shape diamonds that are spectacular. In most cases, what makes one fancy shape diamond nicer than another is all about the diamonds “cut”. But the “cut” that makes a fancy shape diamond spectacular almost never has anything to do with Polish and/or Symmetry.

In my personal experience, I often prefer fancy shape diamonds in which the Polish and/or Symmetry is only “Good”. Many times I find that the fancy shape diamond that has “Good” polish and/or symmetry is much more beautiful than another fancy shape diamond that is Very Good or Excellent.

This is not to say that the fancy cut diamond is more beautiful because the Polish and/or Symmetry is only “Good”. It is because the Polish and Symmetry is usually inconsequential to the big picture – which is “How beautiful is the diamond?”.

Unfortunately for the consumer, the Polish and Symmetry grade on a grading certificate does not give even the slightest inkling of whether or not a particular diamond is beautiful. The beauty of a fancy cut diamond is about the proportions of things such as length by width – or the depth and table. It is about the brilliance and “life” of the diamond. It is about what the diamond looks like when you actually look at it as opposed to looking at a grading report!

The overall beauty of a fancy shape diamond has nothing to do with Polish and Symmetry. Most fancy shape diamonds have Polish and Symmetry grades of “Good” or Very Good. Unlike Round diamonds in which “Excellent” or “Very Good” is more common, a grade of Good” in Polish and/or Symmetry is the “norm” for fancy shape diamonds.

This is one of the issues of buying a diamond online or strictly buying a diamond based on the certification paper. The simple truth that I know after spending a lifetime in the diamond trade is that the beauty of a fancy shape diamond – whether it is a Cushion Cut, an Oval, or an Emerald Cut or any other fancy shape – has nothing to do with the Polish and/or Symmetry grade (except in cases of Fair or Poor). The beauty of a fancy cut diamond is about the diamond itself. It is about how that diamond disperses light.

Unlike a round diamond in which there are scientific parameters when cutting which provide for maximum brilliance, there is no scientific formula for cutting a fancy shape diamond. Most often when cutting a fancy shape diamond, the diamond cutter is working within the parameters of the rough diamond that he starts with and the beauty of the finished diamond is the direct result of the diamond itself.

The creation of a fancy cut diamond is similar to the work of a sculptor. A diamond cutter cuts the shape and dimensions from a rough diamond that has been extracted from the earth. Trust me in that the minor detail of the facet alignment or the smoothness of the surface is inconsequential to the overall appearance of this diamond. A sculptor may achieve a beautiful smooth finish that one could say is “Excellent” or “Very Good”. But that may overlook the fact that the sculpture is ugly!

The bottom line is this. Stick to “Excellent” and/or “Very good” in a round diamond. And understand that in a fancy shape you are fooling yourself if you think that the Polish and Symmetry grade gives you any inkling of the beauty of the diamond.

One thought on “How important is Polish and Symmetry in a Diamond Certificate?

  1. Lorena Medina

    Thank you for the very informative report on polish and symmetry in a fancy cut diamond. It has really helped me on deciding what I want to focus on when searching for my diamond. My search is for a princess cut above 7 mm whether it be under 2ct or at. I would like it to be G or higher in color. SI1 or SI2, polish: very good symmetry very good to good. Depth and table around 70%. And like you said I would like it to have life and to disperse the light in as brilliant as it can be. My budget is 12,000. Maybe I am being unrealistic. Any comments would be appreciated!


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