I think we can all agree that we’re captivated by diamonds simply because of THE sparkle! No other gem can radiate like a diamond does. It’s like a reachable, wearable star that connotes a timeless bond. And the head honcho behind this mesmerizing shimmer is what we call the “Diamond Cut”.
Now, a lot of you may have heard of round cut, princess cut, and other diamond shapes that are tailed by the word “cut“. Well, it’s just like a childhood nickname you can’t get rid of! But that’s not really what Diamond Cut is all about.
What I mean by Cut is the proportions of the diamond that determine its level of sparkle. Or in gemological terms: its fire, brilliance, and scintillation. (You’ll be seeing these terms down the line, so better get used to it. 🙂 ) While the Diamond Shape only refers to the outline of the stone.
Unlike the superficial impression on diamonds and the in-your-face depiction of shape, the diamond cut is technical, measurable, and adjustable to maximize your gem’s brilliance! In fact, the cut is the ruler of the Diamond 4Cs – cut, color, clarity, and carat weight.
Cut is Always King!
Before I begin, please bear in mind that the diamond cut only refers to the proportions of the round and princess cut gems. Therefore, you will not find any cut grades for other diamond shapes.
Now, the picture on the left depicts the relationship between various facets and angles that play as decisive factors in determining the diamond’s cut.
A proportioned cut will let the light traverse through the diamond in such a way that it will be reflected back to the viewer’s eye and give boost to the other 4Cs.
The Diamond's Light Performance
In fact, a well cut diamond will reflect more light and appear larger than it actually is. It can also make the face-up color look brighter, and at the same time, mask or camouflage inclusions. This is because a well cut diamond has greater brilliance, fire, and scintillation that can easily conceal flaws.
Here’s the Science of Sparkle in a Nutshell:
- Fire – The light dispersion that appears as flashes of rainbow colors. It’s beautifully seen on darker environments like at a candlelit dinner.
- Brilliance – The light reflected in and out of the diamond. Having perfect proportions will prevent light leakage and thus, make the gem appear brighter.
- Scintillation – The pattern of dark and light facets that intensely sparkles when the diamond is moved. It’s usually seen in office lighting environments – opposite of where fire can be seen.
See the difference between a perfect cut and an inferior cut in action by comparing these gems:
By clicking the images, you can actually view the diamonds from all sides and see how they differ in light reflection. The one on the left is within super ideal cut proportions and exhibits a lot of sparkle. The diamond on the right however, looks much less lively and exhibits considerably less sparkle.
Another important factor in deciding how well the light will reflect back to the viewer is the pavilion angle. If it’s too shallow or too steep, it will then cause less light return.
Apparently, everybody wants brilliance (white light) and fire (rainbow color light) in a diamond. But if for instance, you have a preference for fire, you can deliberately choose one that maximizes fire. In such a case, you would have to find a so-called “fiery ideal cut diamond”.
Take a look at these 1 CARAT G-VS2 EXCELLENT CUTs below:
The diamond on the left exhibits much more fire than the diamond on the right. The second gem looks great, but it is maximized for brilliance and not fire. Of course, you will only be able to see the difference if you view them from all sides just as you would in real life.
What the examples above are meant to show you is how much of an impact the diamond cut has that it should be your absolute priority in choosing a diamond. You may compromise on everything else, especially on color and clarity, but you should never compromise on cut!
So, Why Do Poor Cut Diamonds Exist?
You would think that people wouldn’t be interested in buying poor cut diamonds where fire, brilliance, and scintillation hardly exist. After all, this is what we buy diamonds for!
But in reality, poor cuts exist for various reasons:
Obviously, people will pay the most attention to the carat weight as it’s usually the first thing you’ll be asked about upon being engaged.
Thus, the prices sharply increase for bigger carat weight than for a better cut. For this reason, many diamond cutters are intent on preserving as much weight during the cutting process.
If a cutter produces a deeply cut gem, more weight will be hidden in the diamond. And it will drive the carat weight and the price higher! Yes, the cut grade will go down, but in most cases, it pays more for the cutter to opt for a bigger carat.
Furthermore, it also happens very often that diamond cutters would want to eliminate a striking inclusion. They do so by cutting it out. But since they also want to preserve more weight, they would risk the diamond cut quality being reduced.
The Different Cut Grades – Which Grade to Choose
Some first-time seekers are duped by fake or unreliable grading reports because they don’t know that you should only look for gems graded by GIA or AGS.
Diamond certificates from other grading companies, especially in-house grading reports, are not as accurate and consistent as the said labs. So, to avoid the hassle, simply filter your diamond search with GIA or AGS stones.
An AGS 0 isn’t equivalent to a GIA Excellent. Still, they’re both great indicators for cut quality. My top recommendation is to go for the best cut! This means that you should choose a GIA “Excellent” or an AGS “Ideal”. In my opinion, the diamond cut is the wrong place to try to save money!
You should only do so on color and clarity as they don’t need to be the highest grades to be the best.
Now, if you are really tight on budget, it’s okay to choose “Very Good” for GIA diamonds or “Excellent” for AGS. These grades will still be good, but the increase in brilliance when going for the best cut grade is, of course, much noticeable.
Visible Differences Between Cut Grades
Diamonds with lower cut grades usually look worse than diamonds with higher grades.
Here's how each rating differ:
Note: Fair and poor cut grades are so disastrous that most shops don't even sell them!
Another thing you have to bear in mind is that there can be considerable differences between diamonds with the same cut grade. Check out the comparisons below!
Excellent Cut Round Diamonds
Both diamonds below are graded “Excellent” by GIA. The one on the left has perfect proportions, while the second diamond's table is too wide making it reflect less light.
Very Good Cut Round Diamonds
The next two diamonds below are both graded “Very Good” by GIA. The one on the left has exceptionally good proportions for its cut grade. The gem on the right, on the other hand, might be considered below average for the “Very Good” cut grade. While it’s still an acceptable choice, I would recommend opting for the diamond on the left.
Good Cut Round Diamonds
The next two diamonds are “Good” cuts. The one on the left is poorly cut and the diamond on the right is a complete mess. Thus, none of these diamonds are acceptable.
As you can see, even if two diamonds share the same grade, they don’t have to appear the same. This is because GIA and AGS allow a certain level of variation as long as it's within the specific grade.
You’d probably deem symmetry as the more evident distinction and assume that it causes the rise and fall of cut quality. But a diamond that isn’t symmetrical can still be brilliant as most of the diamond’s brilliance is produced by the cut and not the symmetry.
An excellent cut and an excellent symmetry go hand in hand. But it’s mainly the proportions between different parameters that determine the diamond’s brilliance. And knowing of these proportions will let you find the best diamond within the same cut grade. It's high time we delve into these features!
Table Size The top horizontal facet of the diamond. Total Depth The diamond’s overall depth from the surface of the table to the culet. Pavilion Depth The lower portion from the bottom edge of the girdle to the culet. Pavilion Angle It is the average of the angles formed by the diamond’s pavilion main facets and its girdle plane. Crown Height The upper portion, from the top edge of the girdle to the table. Crown Angle The angle that’s formed where the bezel facets meet the girdle plane.
The horizontally projected distance from the point of the star facet to the edge of the table, relative to the distance between the table edge and the girdle edge. Girdle Thickness The middle portion of a diamond, a narrow section separating the crown from the pavilion, and functions as the diamond’s setting edge. Lower Girdle This ratio is measured by calculating how long the lower girdle facets are relative to the length of the pavilion. Culet The small facet at the bottom intended to prevent chipping and to the point.
Now, all these parameters must lie within certain limits to get a specific cut grade. Our grading system today is very close to the Tolkowsky Ideal Cut which was introduced by the mathematician and renowned gemologist Marcel Tolkowsky in 1919.
He published his findings for the perfect diamond proportions in his thesis entitled “Diamond Design, A Study of the Reflection and Refraction of Light in a Diamond.”
Today’s Standard Diamond Grading System
Nowadays, GIA and AGS have slightly modified Tolkowsky Ideal Cut’s proportions for diamonds with Excellent/Ideal light performance.
You can find the values on the right.
Although please bear in mind that these values should be used as a basic guideline. If you want to know the perfect parameters specifically for a round cut, please read my post on round diamonds here.
And if you happen to have your diamond's parameters at your disposal, I would advise to type in these proportions into the free GIA facetware tool.
This will quickly tell you what cut grade GIA would rate your diamond!
The proportions on the left usually serves a diamond with an Excellent/Ideal cut grade (AGS is stricter than GIA in cut grading).
However, if you want to have a super ideal cut, then take note of these parameters:
Viewing the Diamond Sparkle in HD
As light travels in and out of the diamond and springs back into the eye of the beholder, the “bling factor” is then created. It's great to know of the specific proportions, but it's also paramount to view your diamond and inspect it from all angles.
Currently, James Allen is the only diamond vendor that will allow you to view diamonds in 20x magnification through their revolutionary 360° video display technology. Another fascinating thing is that their advanced filter tool can turn the intricacies of diamond hunting into just a few taps!
Read Next: Diamond Symmetry
Should you have any questions about Diamond Cut, let me know in the comments section below.
Or might as well write to me, my advice is free. 🙂