Taking A Closer Look At Diamond Polish & Symmetry

Author Sue Davidson, G.G.
Date Feb 17, 2015

Taking_A_Closer_Look_At_Diamond_Polish__(1)Most loose diamonds from reputable sellers will come with a certification from grading labs such as GIA or AGS. These certificates help to grade diamonds so they can easily be compared against one another and so that you can find out everything there is to know about a certain diamond.

Within this certificate, there is a wealth of information, and it can seem overwhelming at first glance. You can start by understanding the basic four Cs of the diamond, such as its color or clarity. Then, you'll want to move on to the more advanced details.

Polish and symmetry grade are two parts of a certificate that you can look at to further evaluate the worth of a diamond beyond the basics. The evaluation of polish and symmetry are important in determining the overall cut grade of a diamond. For a diamond to qualify for an excellent cut grade, both the polish and symmetry must be very good or excellent.

Diamond Symmetry

In gemstones and diamonds, symmetry refers to how precisely the facets of a diamond align and intersect. This can include extra or misshapen facets, off center culets and tables or wavy girdles. Symmetry features can be proportional or facet-related. The science of diamond symmetry can easily become complicated.

There are discussions on accuracy and precision along with symmetry boundaries and non-contact optical scanners. Though technology advances every day, the final results of the symmetry grade are influenced by the objective consensus of independent graders' opinions.

For the sake of gaining a more general understanding, it might be easier to look at a visual. Below are pictures of three different diamonds for symmetry comparison. The diamond on the far left has been given an excellent symmetry grade. The diamond in the middle has the table off center (which means the point of the diamond isn't dead center and the shape is slightly askew), and the diamond on the right has misaligned facets.


You may want to avoid diamonds with poor symmetry because they have defects visible to the naked eye and may misdirect light that travels into the diamond, sending it off at slightly wrong angles and reducing brilliance and light return.

You can always ask, but most reputable jewelers choose not to carry diamonds with a symmetry grade of poor. When comparing two diamonds of equal cut grade, symmetry (and polish) can then be used as a further refinement or tie breaker.

The general appearances of GIA’s five symmetry categories are described for you.

Ranges from no symmetry features to minute symmetry features that can be viewed with difficulty face-up at 10X magnification

Very Good:
Minor symmetry features are seen face-up at 10X magnification.

Noticeable symmetry features are seen face-up at 10X magnification. The diamond’s overall appearance may be affected when viewed with the unaided eye.

Obvious symmetry features are seen face-up at 10X magnification. The diamond’s overall appearance is often affected when viewed with the unaided eye.

Prominent symmetry features are seen face-up at 10X magnification. The diamond’s overall appearance is significantly affected when viewed with the unaided eye

Diamond Polish

Polishing the diamond is the final stage in the diamond cutting process. The polish grade given on a GIA certification refers to the quality of a diamond’s surface condition as a result of the polishing process or to blemishes created after the cutting process.

The polish grade has five categories, like the symmetry grade, and is always performed under 10X magnification. The grades are described as: Excellent, Very Good, Good, Fair and Poor.

A controlled environment and specific standards are followed to maintain consistency with the grading process. Diamond polishing has been done by the hand of the skilled master cutter for centuries. Automatic polishing machines initially appeared in the 1970’s. With new technology and equipment continually advancing the precision of the diamond cutting process, the modern diamond manufacturers can combine the skill of the master craftsman and the advances of technology.

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