Understanding Diamond Cut
As far as we’re concerned, cut is deceptively simple. Cut, unlike other diamond quality factors, is described in layman’s terms-- in simple English adjectives-- not complicated numbers, decimals, or or letter codes. A diamond’s cut can be excellent, very good, good, fair, or poor. Some diamonds receive 3 separate scores for cut, polish, and symmetry, while others receive only two grades for polish and symmetry, but either way, it’s simple. If it’s good, they’ll tell you it’s “good.” If it’s poor, that’s what they call it. Easy.
Photo by GIA.
How those grades are determined is the complicated part, and we’ll get to that in a bit. It has to do with the interplay of a lot of different measurements and proportions. We know it can be stressful shopping for a diamond for the first time, and many people try to self-educate by reading complicated articles about the ideal table percentage range on a diamond, wasting precious hours researching the geometry of gemology when the fact is the answer is there in black and white: if they call it a “very good” cut on the GIA (or IGI or other reputable lab) certificate, a lab of educated professionals has already looked at all the minutia, taken all the measurements, considered all the angles of all the facets and determined that the diamond is… very good. Some labs use different adjectives, like “ideal” instead of “excellent,” but either way, you know what they mean.
This 1.45 ct diamond engagement ring features a beautiful diamond with an excellent cut, excellent polish, and excellent symmetry grading. Secrète chose to showcase this beauty in a retro-inspired platinum setting.
That being said, at Secrète, we love when a simple mission unlocks a passion for learning-- whether it’s the quest for an engagement ring unleashing your inner geologist or the search for a reliable watch inspiring hours of fun nerding out reading about the mechanics of horology-- so we’re happy to open the wormhole into how diamond cut grades are determined.
What Gemologists Look for When Grading Cut
There are seven components to cut grading. The first three are brightness, fire, and scintillation. The remaining four are weight ratio, durability, polish, and symmetry. All seven components are reviewed individually, but the final cut grade is a cumulative assessment on the overall appearance of the diamond’s cut, not simply an average of the seven scores. The reason for this is that each of the seven components interact with each other, making it impossible to grade each individually. There are many different proportion sets that create good looking diamonds.
The first three of the components of cut are about the appearance of light: brightness has to do with how much light is reflected from the diamond (how brightly it shines), fire is about how the reflected light is dispersed into different colors in the spectrum (how well the diamond acts as a prism), and scintillation is the way the light looks when the diamond is moved (how well it sparkles).
Anatomy of a diamond cut. Photo by GIA.
The next four take a lot more into account.
Weight ratio is about how big it looks. A carat is a weight measurement, not a distance measurement, so it’s possible that two diamonds weighing the same amount won’t look the same size from the top if one is cut too deep or the other too shallow. There’s a happy medium where a diamond is cut shallow enough to show off its size but deep enough for the light to bounce around in an appealing way inside. Durability has to do with things like how thick the girdle of the stone is-- too thin and it can easily break-- and other cut characteristics that might make the diamond susceptible to damage with normal wear. Polish is about surface characteristics of the cut, that the diamond has been polished well for high-shine. Symmetry is an assessment of the top-view symmetry of a diamond.
As far as the ratios go, what length or percentage the table should be, what percentage the depth should be the pavillion angle, the crown angle, etc, etc, etc, these things matter a lot, but none of them mean much on their own. A diamond is a 3D shape, so the depth that might work well for one diamond based on all its other measurements and angles may not be the best depth for another diamond based on its measurements. We’ve had young customers who’ve been trying to do their due diligence send us emails wanting to know what the table size was on the diamond we showed them. We’re happy to provide that information to curious customers, but even to a gemologist, table length data alone is useless. What matters goes back to the basics-- that a team of pros at a lab took every measurement and considered multiple factors in conjunction with each other decided that the diamond was excellent, very good, good, fair, or poor.
Here is a side-by-side comparison of the measurements of two diamonds, both 1.00ct, both G color, both VS1, both No Florescence, both Excellent cut, Excellent polish, and Excellent symmetry. Notice how their proportions are a little different from each other, even though they have identical grades? That's because there are multiple percentages and measurements and angles that can create excellent cuts.
What difference does the cut grade really make?
When considering the 4Cs of diamonds, for most people, it becomes a discussion about compromise and where to sacrifice. Should we get the bigger diamond that’s a little less white? Or a whiter diamond with more inclusions? Or a diamond without the best cut grade if it means we can get a higher clarity?
For a simple, minimalist design like this beautiful internally flawless three-stone ring from Secrète's catalog, cut makes a difference, especially the symmetry of the emerald-cut in the center.
We don’t think cut should take the #1 priority, but it should contribute to your decision. Cut grade affects how well your diamond sparkles and its proportions visually, but sparkle and appearance are also influenced by the other of the 4Cs-- an excellent cut diamond with lots of inclusions won’t have the fire and scintillation you’d expect from an excellent cut-- simply because spots and clouds interfere with the way light acts in a stone. While “triple ex” (excellent cut, excellent color, excellent clarity) paired with a nice color and clarity is amazing, very good is also very good, and good is… well, good! It all depends on what you want and need. We’ve even seen fair and poor cut stones look beautiful-- sometimes older heirloom diamonds don’t quite “make the cut” but their charm and vintage look outweigh their less than perfect grades.
This unique, minimalist engagement ring featuring a 1.25ct F color VS2 diamond is available at Secrète's DuPont boutique. Because it's an excellent cut stone, it flashes beautiful light
Our expert team at Secrète Fine Jewelry in Bethesda, MD, and Washington, DC can help you navigate your options to make sure you get the right diamond for your engagement ring or custom jewelry. Contact us today or visit us in the Wildwood Shopping Center or our DuPont Circle store to find the best diamond for you.