Understanding Diamond Cut

As part of our blog series on the 4Cs (cut, color, clarity, and carat), Secrète Fine Jewelry presents our guide to understanding diamond cut.

What is 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, right? 

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. 

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).

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 the 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. According to GIA: 

“The whole is greater than the sum when it comes to a diamond’s proportions, which are the dimensions and angles of a polished diamond’s facets and how they relate to one another. There is no set “formula” or set of proportions that result in a perfectly cut diamond. All of the numbers you might have heard other people referring to – table size, crown angle, pavilion angle – work together to create the spectacular stone sitting in front of you… The GIA system places more emphasis on the overall appearance of the diamond, as opposed to any single set of proportions.” –GIA

The diamond buying process can be intimidating, and sometimes nervous buyers try to self-educate to quell their fears. We’re happy to provide all information to curious customers, but sometimes we know someone is drowning in a Wiki-hole when they start asking for individual ratios. It’s important to understand that measurements and ratios, on their own, do not mean anything, not even to a graduate gemologist; the measurements only matter when considered in relation to each other for their overall prismatic effect. What matters goes back to the basics– a trained laboratory full of educated professionals has already gathered the data and calculated the results, and then they put it in plain English. These grades are the cumulative results calculated by educated professionals in a controlled laboratory, so instead of worrying about the individual numbers that factored into the calculations, you can trust that the grading lab knows more about cut grades than anyone and simply sit back and admire the diamond’s sparkle. 

 

The truth about cut is that it’s complicated! The interrelations of all the little measurements and angles that create that sparkle involve a specific mastery of the geometry of gems. There’s also a lot of misinformation about cut out there. Some bloggers will claim that a diamond’s table percentage, for example, should only be between X% and Y%, but without knowing the other measurements and proportions of the particular stone, it’s impossible to make that claim or to judge a ratio out of context. The easier and more accurate thing to do is to trust the trained experts at the lab: if they said it’s a very good cut stone, it will in fact, be very good; they’re not lying!

Cut and fancy shapes

As we mentioned before, GIA, IGI, and other labs do not assign an overall cut grade for fancy shapes (any diamond shape other than round). For ovals, emerald-cuts, princesses, Asschers, heart-shapes, marquises, cushions, and all other shapes, you’ll simply receive the polish and symmetry grades on the report. Some mega-jewelers will allow you to search for an “ideal cut oval” on their websites, but that’s like someone trying to sell you oceanfront property in Nebraska. If you’re talking about the reality of gemological reports, it just doesn’t exist.

The absence of an overall cut grade for fancy shapes doesn’t mean that the way a fancy shape diamond is cut doesn’t affect its overall look. Ovals, for example, can have a dark zone in the middle called a bowtie that comes from the placement of its facets. Some cushion modified brilliant cut diamonds have too many extra little facets, giving them a flat glittery look instead of a classic diamond sparkle (jewelers call these cushions “crushed ice.”) “Crushed ice” and “bowtie” are not gemological terms, but they’re real considerations for buyers of those shapes. 

Super ideal cuts, super-duper ideal cuts, etc?

Sometimes marketing techniques at online jewelry mega-stores can make people believe their diamonds are somehow “a cut above the rest.” A few well known retailers use jargon to imply that they offer diamonds with cuts beyond “excellent,” referring to them as “super-ideal,” “Astoria excellent,” or some other trademarked term. They may even laser etch these brand-names of cuts into the girdle. Unfortunately, there is no secret extra level beyond excellent for super-duper pretty diamonds. 

If the diamond is graded by GIA, it will either be “excellent,” “very good,” “good,” “fair,” or “poor.” If it’s graded by IGI, it will be “ideal,” “very good,” “good,” “fair,” or “poor.” When a jeweler describes their stones as beyond excellent cut, it’s just a gimmick. A quick glance at the GIA report will confirm that no diamond in the world ranks higher than a GIA excellent. In reality, the companies who use these gimmicks don’t employ any diamond cutters, they don’t have a secret category on their diamonds’ reports, they don’t know about something the GIA doesn’t. 

We believe this type of practice is dishonest because it tries to deceive customers into confusing trademarks with the independent laboratory reports. Independent laboratory report results must be presented clearly, without misleading and inflating jargon, to ensure that consumers can make educated purchases and trust that the diamonds they purchase are exactly as described. At Secrète Fine Jewelry, we describe our diamonds using the language on their certificates, that’s it. No gimmicks. No hyperbole. No cuts that don’t exist. Just the facts. 

How big a difference does cut 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? 

We don’t think cut should take the #1 priority only because all parts of a diamond’s grade work together to make it beautiful, but cut should definitely 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. There are always exceptions to the rules. Sometimes antique and heirloom diamonds don’t quite “make the cut” with poor symmetry and chunkier facets, but their charm and vintage look outweigh their less than perfect grades. Every diamond is unique, so it’s good to look at each one for what it is, its combination of pros and cons, and decide which is the most beautiful to you. 

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.