Diamond Symmetry: What it is, How it’s Graded

Diamond Symmetry & How It's Graded

One of the finer points of examining a diamond for quality is its symmetry. 

Symmetry is the term used when we think about an object with uniform proportions.

For diamonds, it has a more specific meaning.

So I’ll share everything you need know about diamond symmetry and how it’s graded, including:

  • An overview
  • Types of imperfections related to symmetry
  • How it compares to polish
  • Effects on price
  • How to factor in symmetry when choosing a diamond

Let’s dive into these details.

What is Diamond Symmetry?

Diamond Symmetry Infographic Diamond symmetry refers to the alignment and shape of facets. This can affect the brilliance, shape, and overall quality of the diamond. Proper symmetry results in better light performance because it can travel through the diamond without being misdirected along the way.

For a closer view of facets, check out this high-resolution image of a round-cut diamond from multiple angles.

High-Resolution Image of Diamond Facets

Its facets are the triangle- and kite-shaped flat surfaces.

The most pleasing diamonds have symmetrical facets that reflect light and produce the sparkle you expect from the center of an engagement ring.

A diamond with poor symmetry, however, may reflect light in different directions, which reduces its luster.

How is Diamond Symmetry Graded?

The Gemological Institute of America (GIA) scale is one of the most popular organizations that evaluates diamonds. The GIA assigns a rating based on symmetry, polish, and other factors. 

Symmetry is determined by close examination of a diamond under 10x magnification and graded based on the presence and severity of imperfections. 

The GIA rates diamonds in the categories of:

Excellent: Very few, if any, deviations are found within the diamond under 10x magnification. It is as close to perfect as you can typically find.

Very Good: There are slight deviations visible to the diamond’s symmetry with 10x magnification. The defects are extremely difficult to see.

Good: Deviations are more apparent and occur more frequently under 10x magnification. The diamond’s brilliance can start to take a noticeable negative impact.

Fair: Deviations are common under 10x magnification and may be seen to a slight degree with the naked eye. It’s brilliance is significantly affected.

Poor: The diamond has several obvious defects that can be seen with the naked eye. They can appear dull and are often not offered for sale in diamond shops.

Types of Diamond Symmetry Imperfections

1. Table Off-Center

The table is the largest facet of a diamond and is supposed to be central. However, if the table is not centralized this can cause uneven angles in the crown from one side to the other.

The image below (from the GIA) shows an instance where the table is off-center.

Table Off-Center

2. Culet Off-Center

The culet is the bottom tip of the diamond, and it should be found in the center. When examining a diamond through the table, the lower girdle facets should form a perfect square. If the pavilion mains don’t have a centralized meeting point, then the culet is off-center.

Culet Off-Center

3. Out of Round

An out of round imperfection occurs when a diamond doesn’t appear to have the desired round shape, and some areas are squared-off. A diamond should be equal in length and width, but in this case, the two will differ.

Out-of-Round

4. Crown and Pavilion Misalignment

The eight crown and pavilion angles of a diamond should meet in the middle of the girdle at the same point. Misalignment occurs when one of these points has a depth or angle variation. They’re usually the result of other diamond defects such as a wavy girdle or off-center table.

Crown & Pavilion Misalignment

5. Misshapen Facet

A diamond’s facets should be equal in length, shape, and size. In the case of a misshapen facet, one or more will differ from its counterparts, which throws off the symmetry of the diamond.

Misshapen Facet

6. Wavy Girdle

The girdle of a diamond should be continuous straight lines on a flat plane. A wavy girdle means there’s variation in the line trajectory or thickness rather than consistency throughout.

Wavy Girdle

7. Extra Facet

Extra facets can be found anywhere on a diamond but are typically found near the girdle. They’re often placed without considering symmetry, in order to remove inclusions that affect the quality and light performance of a diamond.

Extra Facet

8. Missing Facet

Similar to extra facets, facets are sometimes removed without considering symmetry in order to remove inclusions or small imperfections in a diamond. If a facet is removed, it can affect the clarity of a diamond and result in a lower grade.

Missing Facet

9. Non-Pointing Facet

Diamond facets should come together and meet at a single point within junctions. In non-pointing facets, these points may meet in more than one area or transect through multiple junctions.

Non-Pointing Facet

How Does It Compare to Polish?

Polish and symmetry are key factors to consider with a diamond’s overall quality. They work hand-in-hand but involve different aspects of the gem. 

Symmetry deals with the overall precision and lines of a diamond. Considerations are the diamond’s shape, outline, and the alignment and placement of the individual facets. These factors produce brilliance and sparkle due to properly aligned light transmission.

Diamond polish refers to the smoothness and condition of the surface of a diamond. A well polished diamond will have smooth reflections, and as with symmetry, this plays into its light performance.

Examples of polish features include:

  • Abrasions: scratches or pits on the edge of a facet that result in a fuzzy, white line
  • Burns: Haziness caused by intense heat during polishing
  • Pit: an opening in the diamond that appears as white dot

Polish lines and cut lines on a diamond are almost always present to some degree, but what makes an Excellent (or in rarer cases, Flawless) grade diamond is the depth and visibility of these lines under magnification. 

Symmetry and polish both impact a diamond’s ability to dazzle the eye.

If your diamond is graded by the GIA, its polish and symmetry grades appear in the “Additional Grading Information” section on the left panel of the report.

Symmetry and Polish on GIA Report

Like symmetry, polish is graded on a scale of poor to excellent.

How Does Symmetry Affect Price?

Compared to other aspects of a diamond that impact its appearance, symmetry has a more modest effect on price. You should instead look to carat, clarity, and color if you’re trying to significantly reduce the price.

As a general rule, you can expect a 5 – 10 percent difference in price between each grade for symmetry and polish.

For example, let’s say you have two diamonds side by side, and each are 1.5 carats, VVS2 clarity, an F color, and have excellent cuts. One diamond has excellent symmetry and polish and the other is graded “very good.” 

If the first diamond costs $10,000, you can expect the latter to cost between $9,000-$9,500.

So how this should affect your purchase?

Its overall cut grade is one of the most important factors in a diamond. A quality cut can result in a brilliant diamond. Compromising in this area can lead it to appear dull.

I always recommend choosing an excellent cut diamond. It’s worth the premium. In most cases, excellent cut diamonds also score that grade for polish and symmetry because those aspects are taken into consideration for its overall cut grade.

Should You Consider Symmetry When Buying a Diamond?

Symmetry plays an important factor in a diamond’s performance. 

Although slight differences in the quality of its symmetry might not always be apparent to the naked eye, aim for an excellent grade. At the very least, opt for one that earned a very good symmetry grade but still an excellent cut overall.

I chose an excellent cut for my wife’s round-cut diamond engagement ring, and I’m glad I did. That choice is apparent when it’s viewed because of the way it sparkles.

By examining the grading report and how its facets are aligned, you’ll land on a diamond with the right symmetry grade.

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Jacob Clarke

Jacob Clarke

Jacob Clarke is the founder of TeachJewelry.com.

He earned an Applied Jewelry Professional Diploma from the Gemological Institute of America (GIA) and now brings you essential information about diamonds, settings, and more.

Jacob has consulted with leading jewelry brands, and his work has been cited in Clean Origin, Diamond Nexus and industry publications.

He's also a member of the International Gem Society.

He enjoys discussing jewelry with readers, so contact him with any questions at jacob.clarke@teachjewelry.com.

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Jacob Clarke

Jacob Clarke from Teach Jewelry

About Me

Greetings, my name is Jacob and I am the founder of Teach Jewelry. My aim is to guide you in making informed decisions when it comes to diamond and engagement ring selection. I provide comprehensive yet accessible advice and tips to ensure clarity, eliminating any concerns of overpaying for your diamond, engagement ring, or other jewelry. Whether your interest lies in selecting a top quality diamond, choosing its ring setting, or exploring other jewelry pieces, rest assured, you will attain the knowledge needed to select the right piece with confidence.

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