The Ultimate Guide To Understanding Diamond Symmetry


When it comes to a diamond grading report, polish and symmetry are essential characteristics that define where the stone sits on the scale.

However, the appearance of a diamond can often be deceiving. While it may look refined and polished, this could mean that it’s been sourced from an unethical mine and illegally traded.

In fact, polished diamonds can be sold to unknowing traders by sources that aren’t members of the professional diamond trade. This means that there is a high chance these diamonds have come from conflict and bloodshed.

Let’s take a look at what diamond symmetry is and how you can understand it better. The more you know about the refining process of a diamond, the better you can choose to shop conflict-free.

What is Polish and Symmetry Grading?

Polish refers to the condition and overall smoothness of the diamond’s surface. This will typically be the result of the polishing process that was implemented by the cutter.

When talking about diamond symmetry, this refers to the general outline, the preciseness of shape, and placement of small individual characteristics.

GIA, or the Gemological Institute of America, found that diamonds which had a symmetry grade of ‘good’ weren’t as popular among clients, despite the ‘excellent’ grade they received for the cut.

As a result, GIA has implemented a rule that states the cut grade of a diamond can only be one level higher than the rating it receives for its symmetry.

Ultimately, this means that just because a diamond has received an ‘excellent’ grade rating doesn’t mean that it’s perfect in appearance. In fact, as was mentioned previously, a perfect appearance can often indicate how the cutter attempted to hide the diamond’s original appearance in order to conceal its source.

Polish Features on a Diamond

Almost every diamond that’s been cut will still have signs of being polished on the surface. If the diamond has an ‘excellent’ polish rating, these marks will only be noticeable under magnification.

Let’s take a look at some other characteristics that can be found on a polished diamond:

Nick: small nicks or notches that are located on the girdle junction.

Scratch: a translucent looking faint white line that will be visible on the surface.

Pit: a slight opening on the surface that will look like a pinpoint.

Burn Marks: a hazy white layer caused by a jeweler’s torch.

What Are Diamond Symmetry Flaws?

When someone is polishing a diamond, their goal is to get as much value as they can out of the rough. This is why sometimes the appearance of symmetry can indicate that the diamond has been poorly cut – but it’s a big misconception.

Unless the diamond has been poorly sourced and deliberately manipulated, genuine mistakes made during the diamond cutting and polishing process are rare.

Cutters may even purposely create flaws or characteristics in a stone sometimes in order to achieve their ideal weight.

The logic behind this theory is that diamonds which have good symmetry and weigh 1 carat are much more valuable than diamonds with an ‘excellent’ symmetry rating that weighs in at 0.96 carats.

What Do the Individual Symmetry Grades Represent?

In a gemological lab, polish and symmetry receive their grade based on their appearance under 10x magnification. A microscope is first used to determine their rating before its finally assessed with the naked eye.

Let’s take a look at GIA diamonds and how their grading system works.

GIA Diamonds Polish Grading

Excellent: A very low level of insignificant features that can be picked up underneath 10x magnification.

Very Good: Polish features are noticeable and face upwards underneath 10x magnification.

Good: Features are apparent and noticeable underneath 10x magnification. The diamond’s luster could be affected.

Fair: Features are incredibly obvious and easy to spot underneath 10x magnification. Diamond luster is affected.

Poor: Features are distinct that can be seen even with the naked eye. Diamond’s luster is seriously affected.

GIA Diamonds Symmetry Grading

Excellent: Either a complete absence or incredibly small flaws that are only detected underneath 10x magnification.

Very Good: Very minor flaws in symmetry that can only be detected underneath 10x magnification.

Good: Quite noticeable flaws and features can be detected underneath 10x magnification. Regular visual appearance could also be affected.

Fair: Obvious visible symmetry issues can be easily spotted underneath 10x magnification. Visual appearance is definitely affected.

Poor: Serious issues that can be observed even without 10x magnification. As a result, visual appearance is seriously affected.

Final Thoughts

When it comes to symmetry and polish in a diamond, GIA takes its job very seriously.

Only those companies who have binding contracts with each of their suppliers to source diamonds that are conflict-free are allowed to pass through.

To avoid purchasing diamonds unethically, make sure that your source is a member of the professional diamond trade.