A Simple Guide to Understanding Diamond Cuts
There is so much to learn about when shopping for a diamond engagement ring, or any diamond jewelry – and understanding diamond cuts is one of the most crucial elements of your diamond shopping experience!
Our guide will explain what exactly a diamond cut is, and why you should pay attention to diamond cuts when looking for your next piece of jewelry.
Why Should I Care About Diamond Cut?
Many people are familiar with the 4 Cs of diamond grading — cut, clarity, color, and carat weight. The first one, cut, probably has more confusion surrounding it than any other, and it’s arguably the most significant. Diamond cutting is an incredibly precise and difficult skill that takes many years of training and apprenticeship.
A diamond’s cut grade directly influences all the other grading factors. If a diamond is poorly cut, its color and clarity will suffer and its carat weight might be artificially inflated, adding to the cost of the diamond without providing any more value.
So diamond cut is incredibly important. What does a diamond cutter do? How does a gemological lab evaluate the finished diamond? And why is it so important for us as shoppers to understand this magical process? Read on and find out!
What’s the Difference Between Diamond Shape and Diamond Cut?
Diamond shape refers to the overall idea we perceive when looking at a diamond. For example, this could be round, square, oval, or specialty shapes that fall somewhere in between. It is the broadest, most general definition of the way a diamond is cut and the choice that was made for that particular piece. You can read more about the magic of diamond shapes in our detailed diamond shape guide.
Cut, on the other hand, refers to an entire art and mathematical science made up of distances, angles, and the relationship a diamond has with light. An expert diamond cutter can manipulate the way light passes through the stone, causing it to bend and refract and split up into multicolored sparks we call “dispersion”.
A well cut diamond will have a good balance of light and shadow and brilliance, whereas a poorly cut diamond with unbalanced or badly proportioned facets will look washed out and dull. Every diamond shape has slightly different variables that a cutter needs to know in order to make it come to life.
What does ‘Diamond Cut’ Mean?
To put it simply, diamond cut is the precise combination of symmetry, proportion, and mathematical calculations used to achieve the desired fire, brilliance, and scintillation in a diamond.
That’s a lot of jargon and not a lot of help. Don’t worry – we’ll break it down. First, let’s talk anatomy.
From top to bottom, a round brilliant diamond is essentially divided into three parts:
- the crown (the top half)
- the pavilion (the bottom half)
- the girdle (the “belt” that runs around the center at the widest point)
Each of these parts is further broken down into a series of precise facets.
The crown is made up of the table — the largest and most prominent facet on the very top — as well as smaller ones called star, bezel, and upper half facets.
The pavilion is made up of lower half and pavilion main facets, and often a culet (that’s the teeny tiny one right at the bottom, opposite the table).
The girdle may be faceted around the diamond for extra sparkle, or it may be left smooth. Sometimes it is left unpolished which gives it a distinctive frosty look; this is called a “bruted girdle”. To help visualize all these terms, here’s a great chart from the GIA showing the arrangement of diamond facets.
While most people have a general idea of what a faceted diamond looks like, they often don’t know that this particular pattern was chosen for a very specific purpose: sparkle. Or, to put it more simply, light. A faceted diamond is a mathematical arrangement based on very precise measurements and angles so that when light enters the diamond’s surface it jumps from one facet to another, bouncing around like a ping-pong ball.
Sometimes when the light hits one of the facets, it breaks up into individual rainbow colors, or spectral hues. This gives us the multicolored flashes that we in the jewelry industry call dispersion, or “fire”. Sometimes the light will reflect back at us whole, and these flashes of white light are what we call “brilliance”. A perfectly cut diamond will have a balance of both white and colored light coming back at the viewer.
Lastly, some light will not enter the diamond’s interior at all but rather reflect off the faceted surface. When you move the diamond from side to side, you will see the facets brightening and darkening one at a time, making it look like the light is dancing over it. This effect of light and movement is what we call “scintillation”.
The complex combination of fire, brilliance, and scintillation is what gives diamonds their trademark sparkle. And it all comes down to the way a diamond is cut.
How is Diamond Cut Quality Determined?
The industry standard for grading diamond cut comes from the Gemological Institute of America. They grade their diamond cuts as Excellent, Very Good, Good, Fair, or Poor. Another respected gem lab, the American Gem Society, adds one more to their grading system — Ideal.
When shopping for diamond jewelry, ask the jeweler if they have a grading report from one of these labs that documents their findings of the stone.
The cut grade that the lab chooses is based primarily on angles and percentages. Through many years of testing and studying well cut and poorly cut diamonds, the jewelry industry has come up with a range of measurements that fit into each grade. Let’s look at some of these measurements.
The table facet, as we discussed above, is the largest facet on a round brilliant diamond and the one most prominent when viewed from above.
Rather than width and length — remember, this will vary depending on the size of the actual diamond — the table measurement is presented as a percentage of the width of the entire stone. For example, a diamond of one carat will usually be around 6mm wide. If the table facet measures 3.8mm across, that makes it 63% of the stone’s total width. This figure would be presented as a table percentage of 63.
An “Excellent” table percentage ranges from 52% to 62%. If the table is much larger or much smaller than that range, the light gets lost inside the stone and it begins to look dark and washed out.
Remember our three diamond components? Crown, girdle, and pavilion. Now it’s time to measure them in the same way we measured the table, as a percentage of the total length from top to bottom.
For instance, if a diamond is 6mm wide by 3.4mm long, the total depth will measure 56%. If the crown of the diamond — everything above the girdle — is 0.8mm, the measurement will be presented as a crown height percentage of 13%. Then you measure the girdle and the pavilion in the same way.
Professional gemologists do this process for every aspect of the diamond’s shape, measuring each individual facet and how it relates to the larger whole. While it seems mind-numbingly meticulous, gemological laboratories have managed to quantify the perfect proportions for a diamond with the most beautiful optical effects.
Diamonds that fall too far outside this range will absorb light or allow it to pass through completely. They will appear dim and tired with dark shadowy patches, rather than exploding into the fireworks we’ve come to love in our jewelry.
Symmetry and Polish
Other aspects gem graders will look at are symmetry and polish. These are a little more subjective because they’re harder to pinpoint to a numerical figure.
If a diamond’s table has a percentage of 56% (that puts it in the “Excellent” column, remember?), but is off-center or has some longer sides and some shorter ones, it’s going to look awkward and unappealing. Rather than being shown as a percentage, diamonds are given a symmetry grade from Excellent through to Poor based on the grader’s subjective assessment.
Polish refers to the appearance of a diamond’s surface. Careless cutting techniques can leave small abrasions or lines caused by dragging microscopic minerals across the diamond’s surface. Sometimes inclusions near the surface of a diamond might become dislodged in the cutting process, leaving tiny nicks or scratches behind. A gem grader assesses the stone’s polish grade from Excellent to Poor based on its overall finished quality.
Essentially, all aspects of cut grading come down to how well a human being was able to bring the beauty naturally present in the diamond to its absolute greatest potential.
How Does Diamond Cut Affect Value?
As you can see, cut is the most important grading consideration when it comes to a diamond’s inherent beauty. When a cutter approaches a diamond, they need to find the best way to use the most rough stone possible. Sometimes they will cut a deeper pavilion or a higher crown in order to waste less of the material.
While these choices will increase the carat weight of the finished product, the diamond won’t interact with light in the best possible way and the final cut grade will be lower. A well cut, well proportioned diamond will always be more expensive not only because of its visual appearance, but because more rough stone is lost in the cutting process (this is also why some diamond shapes are more costly than others, as you will see in our article on diamond shapes).
When working with a modest budget, we recommend prioritizing the best cut grade possible and allowing more flexibility when it comes to color and clarity grades.
How Does Diamond Cut Affect Other Grading Factors?
The “4 Cs” of diamond grading are cut, clarity, color, and carat weight. Not only is each factor important to a diamond’s beauty on its own, but each one in turn affects the others.
As we’ve seen, cut and carat are fundamentally linked. The amount of stone that gets removed in the cutting process determines the final carat weight. This is why it can be so tempting for a diamond cutter to leave more of the rough stone in the diamond, most commonly in the pavilion or in the girdle — especially when when a diamond falls right on one of those “magic sizes”.
While a thicker girdle or a heavier pavilion will add more weight and more carat value to the diamond, this dead weight will impact the way light passes and is distributed through the stone, resulting in a less beautiful final piece.
Round brilliant diamonds are designed to show the most beautiful optical display of light and color as well as to hide any internal flaws the diamond might have. Well cut diamonds that exhibit a lot of brightness, dispersion, and scintillation will glitter so brightly that minor internal inclusions will be lost within them.
Poorly cut diamonds, on the other hand, may show these clarity characteristics more obviously. Sometimes cutters will also try to position facets or sneak in extra ones to remove inclusions during the cutting process. These choices can negatively affect the final cut grade, even if they raise the final clarity grade.
That same stunning light show displayed by a well cut round brilliant also helps to disguise a lower color grade. The bright white light coming out of a diamond makes it harder for us to perceive off colors in the GIA near-colorless or faint color ranges.
A poorly cut diamond won’t send back as much light, and any undesirable color tones will be more apparent. This means that when we’re shopping, prioritizing the best possible cut grade allows us to save a little bit by going down one or two color grades.
Similarly, specialty diamond shapes that aren’t cut to maximize brilliance will also show off colors more readily.
Diamond Cut FAQ
A perfectly cut diamond will be neither too shallow nor too deep. This graph shows the direction light takes when it enters a diamond that is badly proportioned (although they use the terms “poor” and “very poor” instead of the GIA’s “fair” and “poor, it still presents a helpful visual).
The ideal cut diamond will show a mixture of fiery rainbow colors and glittering, eye-catching white light. It will also have a girdle that’s not too thick and a well balanced, well proportioned table facet between 52% and 62% of the stone’s total width.
While other grading factors have some flexibility, there is very little that can save a poorly cut diamond. When shopping for a solitaire or center diamond, we recommend that you choose a cut grade of Very Good or higher even if it means going a bit lower in other factors.
The GIA specifically developed the diamond cut grading scale to evaluate round brilliant diamonds. They do not provide formal cut grades for any other diamond shape such as oval, square, or specialty cuts like cushion and marquise. The American Gem Society provides cut grades for round brilliant and square or princess cut diamonds.
Because this represents a significant gap in the information a consumer needs when shopping for diamond engagement rings, many jewelers will use their own in-house cut grades. While these are very useful ways of communicating with the customer, these grades are not standardized from one jeweler to another and do not reflect the industry as a whole.
As we’ve seen, a perfectly cut round brilliant diamond brings out the best qualities already inherent in the stone, distributing light and color in a stunning firework display. The reason diamonds have been so prized for so long is because they are the perfect vessel for this; their internal structure interacts with light in the best way possible.
Other gemstones — including diamond simulants such as cubic zirconia, white topaz, and white sapphire — do not share this same quality.
When looking at other faceted gemstones, the stone should look well-balanced and polished with even, consistent facets and a centered table that is not too small and not too overwhelming. The exact angles and percentages of the cut are not as important when shopping for other gemstones as they are when looking at diamonds.
The Art and Science of Diamond Cut
As you can see, diamond cut is an incredibly complex science that plays a huge role in a diamond’s beauty. Diamond cutters are the unsung heroes of the fine jewelry industry, training for many years to coax the fire and brilliance from a diamond in the rough. A misjudgment can ruin the effect of an otherwise high quality diamond, and a single mistake can cost thousands of dollars.
Diamond cut is the base that supports all other grading factors when evaluating diamonds. When shopping for diamond jewelry, cut should always be the first priority. If a diamond is poorly cut, even the most clear, colorless, high-carat diamond will appear lifeless and dull.
Color, clarity, and carat weight, while significant to a diamond’s appearance, will not have any value without a well-cut foundation. After all — these are all inherent qualities a diamond develops within the earth, before ever being set upon by human eyes.
Cut is where raw material becomes art.
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