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What is Diamond Symmetry?

Read how symmetry is defined, measured, and valued by the GIA. Learn how it affects the beauty and value of diamonds

When it comes to the human face researchers have found that symmetry is an important ingredient in beauty. The same is true in animals, whether you’re admiring a resplendent Indian Peacock or a funky Garden Tiger Moth the appeal of perfect symmetry is obvious. But when it comes to diamonds, symmetry can be complicated. Perfect symmetry in a diamond can cause it to be more beautiful than one with less symmetry, but it costs more, and it may or may not be something you can even see. So, how is diamond symmetry measured, and what does symmetry actually mean when we’re talking about diamonds?

Symmetry is the alignment and shape of a diamond’s facets. It’s a measure of how perfectly a diamond was cut. Facets should not only be identical in size and shape, the overall shape of the diamond must be consistent when viewed face up and from its side.

Symmetry can be difficult for the untrained eye to judge. Thankfully, symmetry is already part of a diamond’s cut grade. If you are only considering diamonds with excellent cut grades, you can’t really go wrong when it comes to symmetry. But for the diamond shopper that has gone further down the rabbit hole and wants to understand why two diamonds of similar cut grade have a different price, symmetry can be part of the explanation. Symmetry can influence a diamond’s value by 5-10%.

Symmetry is not only important because it influences a diamond’s value, it is responsible for a large part of its beauty. Perfect alignment of facets can create superior sparkle. Before you place symmetry at the very top of your list of criteria, it’s important to understand that the visual effect of an excellent symmetry when compared to a very good symmetry diamond is still often quite subtle, and difficult to distinguish without a trained eye and magnification.

One piece of advice that you can use with complete confidence, avoid diamonds that have been graded as “poor” of “fair” for symmetry. These diamonds have distinctly noticeable imperfections that are visually apparent and are likely to make your diamond less sparkly.

Symmetry is caused in diamond manufacturing when rough diamonds are cut. Diamonds are cut using sophisticated laser and cnc machines. Their facets are planned in advance by computers, and then the machines do the rest. They are very sophisticated and accurate, so you might wonder where all of this symmetry nonsense comes from. Shouldn’t they all be cut right?

The explanation to this, as with so many things in life, is economical. If the original shape of the rough diamond produces a larger stone by sacrificing some of its symmetry, or a slight adjustment in its shape avoids an imperfection, the diamond will likely fetch a higher price. A diamond cutters job it to produce the most valuable diamonds they can from the rough stones that they cut. Since most shoppers aren’t quite as savvy as you are, educating themselves on the details of diamond cut, they will often overlook slight asymmetry in favor of a slightly larger size or lower price..

Diamond Symmetry Grades

Like other quality factors, the GIA has established well-defined grades for diamond symmetry.

Excellent means that the size and location of the facets are perfect, the location of the other diamond features, like the table and culet, crown and pavilion are all even and located in the correct places. The diamonds shape when viewed overhead is either perfectly round, or with fancy cuts, perfectly symmetrical.

Very Good means that the diamonds faceting is nearly perfect, and only slight imperfections exist in either the location or shape of the facets, but overall the diamond appears generally symmetrical.

Good means that the diamond does have apparent imperfections in the arrangement and shape of the facets, or the location of the other diamond features like the culet or table, which may be off center or misaligned. Likewise the pavilion and crown areas may not be aligned to each other and be off center.

Fair or Poor means that the diamond has noticeable and distinct imperfections. In round diamonds, it is likely that the diamonds width and length are different, the facets may be poorly shaped, and the features of the diamond may not be in the correct locations.

Which Symmetry Grade Should you Buy?

Because symmetry is just one of several factors that determine a diamond’s cut grade, many shoppers will never notice the symmetry grade. A diamond with a symmetry grade of excellent may cost 5% to 10% more than a diamond with good symmetry. If you are looking to save on price you might wonder whether compromising somewhat on symmetry is a good option.

The visual impact of an excellent symmetry diamond compared to a very good symmetry diamond is subtle, and is not likely to be spotted by an untrained eye. The impact in price is less subtle.

Fancy shapes also look better when they have perfect symmetry, and while the location and shape of the facets is entirely different, the concept is the same.

Of the four C’s, a diamond’s cut does have the biggest impact on its sparkle, and symmetry is an important part of a diamond’s cut. It is generally better to make more significant compromises on other factors like clarity or color than opting for a diamond with poor or fair symmetry because it is likely to detrimental to a diamond’s sparkle.

How to Spot Poor Diamond Symmetry?

Without even looking at a round diamond, you might notice the measurements on its grading certificate. If you see a diamond that’s 7.00mm by 7.2mm you will know right away that it’s not a perfect circle.

When looking at the side view of a diamond, you may see that the table is too far to one side. You might also notice this looking at it face up if you have good eyes. This means the diamond is slightly lopsided, and it may affect its sparkle and overall appearance.

When looking at the side view of a diamond, you might notice the culet seems too far to one side or the other, rather than being perfectly centered below the table. This means the entire pavilion is misshape, and is likely to reflect light much differently than it would have if it were perfectly centered.

Table to culet alignment. When looking at the side view of a diamond you might notice that although the table and culet are fairly centered, they are leaning towards opposite sides of the diamond, and it is a little skewed. This will also have an impact on the way light is reflected throughout the diamond.

Crown to pavilion alignment. Looking at the side view of a diamond you may see that the crown angles and pavilion angles are different on either side of the diamond, which will cause it to have a lopsided and inconsistent shape.

Wavy girdle. When a girdle is different thicknesses at different points, it can have a wavy appearance. This is different than a faceted girdle, which is an intentional feature.

Misshapen Facet. When a facet is inconsistently shaped, distorted, or composed of multiple indistinct surfaces, it is misshapen and will not reflect light in a desirable way.