Diamond polish is one of two important attributes that contribute to a diamond’s finish. After it is cut, a diamond’s surface is then polished to make it smooth and shiny.
Every diamond has a polish grade that reflects how well the diamond has been polished. This will affect the overall look and value of your diamond, so it’s important to know what the grades are and which one you should choose.
How Are Diamonds Polished?
Jewelers use a diamond polishing wheel to smooth the facets of the diamond after it is cut. This wheel helps to get rid of any minor bumps or cracks on the diamond so it can reflect light in the most brilliant way.
Different polishing wheels have different grains, which refers to how fine the particles are. The finer the grain, the more polished the stone will look.
Most of the time, the diamond cutter will also polish the diamond. That way, they can make sure they can control the outcome and ensure the diamond’s polish matches its cut grade.
Polish Lines and Other Blemishes
There are many features of a diamond that graders look for when assigning a polish grade. These imperfections vary based on who polished the diamond and how well it was done.
Scratch – A faint white line on the diamond’s surface that doesn’t have depth. Scratches can be polished away.
Nick – A tiny notch found on the diamond.
Abrasion – Small nicks or notches found at facet junctions where facets can be more fragile and susceptible to wear and tear.
Pit – A small pinpoint-like dot on the surface that can be caused by an inclusion falling out of its pocket.
Lizard skin – A bumpy-looking patch on the surface that resembles a rough diamond.
Polish lines – Very faint lines or shallow grooves on the surface.
Rough girdle – An unpolished girdle with rough patches that are hard to polish.
Burn marks –White patches left from high temperatures during the polishing process that are very hard to remove.
Diamond Polish Grades
The Gemological Institute of America is a leading diamond grading institution that assigns polish grades to all certified diamonds.
The diamond polish grade indicates diamond polish quality, which affects the look of the diamond and the price. Graders must consider all the various blemishes and lines on an individual diamond before assigning it a polish grade.
Excellent: No visible polish lines or imperfections can be seen under 10x magnification. This lets light enter and exits the diamond with the most sparkle.
Very Good: There may be very slight imperfections or blemishes on the diamond seen under 10x magnification. These blemishes will have very slight or no effect on the overall sparkle and brilliance of the diamond.
Good: There are visible blemishes or polish lines on the diamond’s surface, which may or may not only be visible at 10x magnification. This affects the ability of light to penetrate the diamond, which will have an effect on the sparkle. The diamond cut grade cannot be higher than Very Good.
Fair & Poor: There are finishing blemishes or polish lines that are visible on the diamond. Typically visible by the naked eye. This limits the diamond’s ability to reflect light. The diamond cannot earn a cut grade higher than Good.
What Diamond Polish Grade Should You Choose?
While it may seem natural to want only an Excellent polish grade, you may not need a polish grade that high to achieve a sparkling, brilliant diamond.
Many trained jewelers cannot tell the difference between Excellent polish diamonds and Very Good polish diamonds, even under 10x magnification.
If there is no visible difference to an untrained eye under magnification, then why spend the extra money for a higher grade?
Even a Good polish grade may not have any visible blemishes. If your diamond ring is simply for you, then it really doesn’t matter if you have a diamond with a lower polish grade.
That being said, there may be differences in the look and shine of a diamond based on each individual diamond. Always check the diamond for yourself if you can, and if it looks good to you, don’t worry about the polish grade.
What is Diamond Symmetry?
Diamond symmetry refers to the shape of the diamond itself, including the placement of facets, arrangement of the facets, and overall outline of the diamond.
A diamond’s symmetry is actually slightly more important than diamond polish when it comes to how your diamond will shine and sparkle.
Diamond Symmetry Grade
Like diamond polish, diamond symmetry is graded. The grading scale is very similar and depends on the number and severity of different forms of imperfections.
Excellent: The diamond’s proportions are perfectly symmetrical and have ideal sizes. The facets are arranged and aligned to produce maximum brilliance.
Very Good: The diamond may have a couple of imperfections affecting the shape and the arrangement of facets seen under 10x magnification. These imperfections do not affect the sparkle or brilliance of the diamond.
Good: The diamond may have slightly disproportionate facets that affect its shine and brilliance of the diamond. The diamond cannot achieve a cut grade higher than Very Good.
Fair & Poor: There are noticeable imperfections in the symmetry of the diamond and facets. This category includes asymmetrical diamonds that may misdirect light.
Imperfections Relating to Symmetry
These are some of the features graders look for when assigning symmetry grades to diamonds.
- Off-center culet
- Misshapen facets
- Off-center table
- Wavy girdle
- Crown and pavilion angle variation
- Non-parallel table and girdle
How Important is Diamond Polish and Symmetry?
Diamond cutters must make a lot of choices when cutting and polishing a diamond. They may sacrifice some features like polish and symmetry grades for other factors.
For example, they may not polish a diamond completely because it would be the difference between a 1.00-carat diamond and a 0.99-carat diamond. Or, the diamond may not be perfectly symmetrical because the cutter wanted to remove large inclusions in a specific area of the diamond.
Sacrificing a little on symmetry and polish is worth it most of the time for these reasons because these sacrifices don’t affect the diamond’s sparkle.
Cut Grade Is More Important
Both polish and symmetry affect how a diamond looks. While these are important features of a diamond’s surface, keep in mind that cut grade is the most important factor to look for when buying a diamond.
Polish and symmetry will ultimately affect the cut grade, but looking at the cut grade will tell you more than polish and symmetry grades individually.
Check out our guide on the 4 C’s of diamonds to better understand how diamonds are graded on cut, color, clarity, and carat weight. Then, you’ll be ready to shop for a diamond engagement ring, tennis bracelets/diamond bracelets, or any diamond jewelry.