We have made it through three of the 4Cs, and here we are at cut—the last, but the most important, of the Cs.

Why, you ask? Well, a diamond’s cut can be like the difference between taking filet mignon and burning it to a tasteless crisp versus searing it to perfection to lock in the juices. A filet is divine by nature of the cut, but it’s all in how you cook it. Or to go back to our car analogy, think of a Lamborghini versus, well, almost any other car. Both cars are made using the same general materials, but they do not yield the same result.

Just a few of the different variations of diamond cuts available on the market today.

The cut of a diamond has come to have two definitions. The first is the style of cut—the actual outline shape and faceting style of the diamond. We went over a number of outline shapes when we talked about carat, but for a refresher, some examples of gemstone shapes are heart, oval, marquise, pear, and, the most popular, round. There are also different faceting styles, even within the same outline shape. For example, a rectangle with stepped (rectangular) faceting is called an emerald cut, while a rectangular shape with brilliant faceting (kites and triangles) is called a radiant cut. The different faceting styles affect how the light returns off the gemstone, giving a single shape a number of different looks.

This diagram illustrates how light is projected within a diamond in relation to its proportions. Deep and shallow cut allow the light to go through the diamond, while an ideal cut diamond will bounce light back out the top, a.k.a. lots more sparkle!

The second definition of cut is how well a diamond is literally carved, so the actual quality of the cutting itself. This is the most important part of a diamond’s cut. This quality factor is not a natural, inherent trait of the diamond like color, clarity, and carat, but one where a human touch defines the diamond’s value. The craftsmanship of the cutter can be seen by how much he or she makes a diamond sparkle, one of the traits that has enamored people to gemstones for hundreds of years. If you have two diamonds with all other Cs equal, for example, the diamond with a higher cut grade will have more light return (sparkle). There are three different parts to light return, though, that affect how a diamond sparkles. These are fire (rainbow effect), brilliance (reflection of white light), and scintillation (contrast of light and dark areas). Each of these characteristics and how much they contribute to the diamonds overall sparkle is directly controlled by how well the diamond is cut. 

So the amount of sparkle a diamond has can clue you in to its cut grade, as we just mentioned, but there is more to it than that. A cut grade is broken down into three parts: proportion, symmetry, and polish. Each aspect can add or detract from the overall light return, and thus, the final cut grade.

So cut grade can be hinted at through a diamond’s sparkle, as we just mentioned, but there is more to it than that. A cut grade is broken down into three parts: proportion, symmetry, and polish. Each aspect can add or detract from the overall light return, and thus, the final cut grade.



A diamond has three parts when you look at it from the side—the top portion is the crown, the middle line that runs around it is the girdle, and the lower portion the pavilion. The crown and pavilion are covered in a number of facets: at the top of the crown is the table (the flat top of the diamond), and the bottom of the pavilion is the culet (the bottom point).

On the left, two smaller but ideal cut diamonds are yielded from a piece of rough. This results in a greater loss of material during the cutting process, but the diamonds will be much more appealing and valuable. On the right from the same piece of rough, two lager carat diamonds can be cut, but they will have a very poor cut grade making them much less appealing and less valuable despite there larger carat size.

Sizing and angling each section of the diamond for a more proportioned cut will allow more light to enter the stone and be reflected back up to the observer, just as you have to angle mirrors and lenses properly in microscopes, cameras, and telescopes to see an image. Some factors that are taken into consideration when determining a cut grade include the angle of the crown and pavilion, the depth of the crown and pavilion, the width of the diamond, the size of the girdle, table, and culet, and their relations to one another.

If the proportions are off, resulting in a diamond that is too deep or too shallow in relation to the width of the diamond, it may appear dark, flat, patchy, or dull when viewed from the top. Diamonds may be intentionally cut in this way in an attempt to save material, though. For instance, a diamond cutter may be given a piece of rough diamond that is shallow or deep, so he or she may choose to sacrifice on the quality of the cut for a bigger stone rather than remove a large amount of the diamond in order to achieve an ideal cut. Thus, a diamond with a good cut is worth much more, not only because of its excellent sparkle, but because a greater amount of material is usually sacrificed to get it.

“Tiffany diamond cutters refuse to make this compromise; when the choice is size or beauty, we always choose beauty.” – Tiffany.com


Tip: Did you know that not all diamond shapes get cut grades from gemology labs like the GIA? Most labs only give cut grades to round brilliant cut diamonds (though the EGL Gemological Laboratory does give princess cut diamonds a cut grade.) To consistently grade the cut of a diamond, thousands of diamonds are analyzed to compare the multitude of proportion variations and the effect of each on light return. Then, each possible variation is given a cut grade by the lab and used for grading. Obviously, this takes a lot of time and resources, so it’s not feasible to do this for every possible outline shape and style as there are hundreds of variations. Many diamond sellers, however, will give fancy-shaped diamonds a cut grade based on a combination of their own experience, its relation to other diamonds of the same shape, and proprietary formulas or generic measurements. While this isn’t data gathered from thousands of diamonds, if you’re working with a jewelry professional that you trust, they can guide you through these non-standardized grading systems to help you understand better. The cut grade is always worth considering.


Imagine two red hearts made out of construction paper. The first heart has two sides that match and are perfectly equal. The second has one wobbly side and one side that is much smaller than the other. Then you wonder why the artist didn’t cut the second heart before their two-martini lunch. This is an example of excellent symmetry versus poor symmetry.

Diamonds with poor symmetry do not return light properly, a.k.a less sparkle. 

The outline, angles, and faceting of the diamond are examined to determine its symmetry, just like with the hearts. If the outline is off, everything else will be off. If the crown or pavilion angle is not the same all the way around, the facets will be off. If a facet is incomplete, missing, extra, doesn’t line up, is larger or smaller than the others, or is not perfectly shaped (the table should be an octagon on a round brilliant, for example), then the surrounding facets are affected. Symmetry characteristics can range in severity, but the more incorrect they are, the less light return there is, and the lower the cut grade will be.



A poor polish on a diamond can look cloudy, have chips, rough edges or worse.

You know what polish is, that final swipe of the bathroom mirror after you’ve just cleaned it, which may or may not have left a bunch of streaks behind. The same thing can happen when polishing a diamond, but unlike the bathroom mirror, it can’t just be wiped away on a second try. A poor polishing job on a diamond can result in a number of polishing lines, burn marks, abrasions, scratches, pits, nicks, or a rough girdle. As with your bathroom mirror, you want a clean, smooth surface for better reflection. And as with symmetry, the cut grade for the polishing portion of a diamond’s cut depends on the quantity—or how many “mistakes” in the polishing there are—of polishing characteristics.


These three factors—proportions, symmetry, and polish—are taken into consideration when determining a stone’s overall cut grade. On some certificates, like those from the Gemological Institute of America (GIA), symmetry and polish are given a separate grade that can affect the overall cut grade. Diamonds called Triple X’s have Excellent cut, polish, and symmetry grades. A diamond with a Very Good polish can still receive an overall Excellent cut grade, but cannot if the diamond has Good polish or lower. Thus the final grade cut grade is a result of an average of the three grades given to proportion, symmetry and polish.

Multiple grading systems and terms exist for cut grades, including Select Ideal, Ideal, Signature, Premium, Hearts and Arrows, Excellent, Very Good, Good, Fair, and Poor depending on which lab or grading system is used. This can be confusing, so if you don’t know where a given cut grade stands in the grading system, ask the jeweler to show you the entire grading scale being used. This will help give you a better understanding of what each grade in the system means so you can see where that diamond you have your eye on falls on the scale.

Now all you need to do is figure out what style of ring to get! *wink*

There are also signature and branded diamond cuts that may or may not be better than the standard cuts we’ve talked about; it all depends upon the grading criteria. As always, not all grades are equal, and you may not be comparing apples to apples if the grading source differs.

When diamond shopping, cut is the most important thing to consider, especially if shopping for a round brilliant cut diamond, which is most closely defined by cut grades. When considering a fancy- or older-cut style diamond, the grading system may not seem as important since there is no industry standard for these types of cuts. But by comparing diamonds side by side—round brilliant cuts included!—you’ll soon be able to see which diamonds sparkle more and appeal to your eye the most. When purchasing a round diamond, it’s best to purchase a stone with a Good cut or higher. This way you will get the best return-on-investment for your diamond, plus all that sparkle and a lot of ooohs and aaahs!


Go Back: Dissecting the 4Cs – Part I: Carat

Go Back: Dissecting the 4Cs – Part II: Clarity

Go Back: Dissecting the 4Cs – Part III: Color


Bye for now,

Alicia Gardner Kozikowski, G.G.