By now, you should know cut is one of the most crucial factors when it comes to selecting a diamond. Before we get into more serious stuff, I want to share a little history about the evolution of diamond cut grading.
Back in 2005, GIA was the first gemological lab to create the grading system and they were also the first lab to introduce the concept of having a cut grade in round diamonds.
Since then, other gemological labs started to develop their classifications for cut grading. Most notably, the American Gem Society (AGS) Laboratory created a numerically based cut grading system that assesses the light performance of a diamond.
Today, we have reached a stage where scientific research has enabled us to estimate the brilliance and beauty of a diamond based on its proportions. One such tool developed by GIA is the FacetWare Cut Estimator.
Registration for an account is free and the tool is available to the public. Once you are logged in, you can plug in the numbers from the grading report and get an instant estimate of the diamond’s cut grade.
First of all, let me be extremely clear about grading labs. The ONLY diamonds you should buy are those graded by GIA or AGS. If you buy a diamond graded by any other lab or has an in-house “certification”, you can expect to get ripped off because of inflated ratings.
It’s as simple as that.
GIA and AGS are the world’s leading authorities in diamond grading and they offer consistent grading standards. When it comes to cut grading, this is how diamond cut is presented in a GIA and AGS diamond grading report respectively.
While GIA and AGS may use a slightly different system to assess diamonds, there is one thing that is ubiquitous. The overall optical performance a diamond displays is a key component in determining its cut grade.
Without getting into the nitty gritty details here, I highly recommend you stick to a minimum cut grade of Excellent and settle for nothing less.
STAY AWAY from Good/Fair/Poor categories. Don’t throw your money down the drain by buying poorly cut diamonds. In fact, you are far better off purchasing cheap simulants than spending money on a diamond that doesn’t sparkle well.
I don’t know about you but when I’m buying a diamond, I only expect to buy diamonds with the BEST sparkle and brilliance. I personally set extremely high standards for cut quality and I suggest you do the same when shopping for an engagement ring.
Let me interpret the different ratings and explain them in layman terms for you:
The majority of the diamonds in the market are cut to garbage standards and the GIA cut scale classifies them in a “polite” manner. If a diamond doesn’t have an Excellent cut rating (GIA) or Ideal cut rating (AGS), don’t even bother wasting your time on it.
Now, you might be wondering if the “easy” way to pick a diamond would be to choose one from the Excellent or Ideal cut rating category. However, the problem here is that the GIA cut grading system is very broad and you get a wide range of cut quality even in the triple excellent range.
Comparatively, the AGS cut grading system is more stringent and robust but you will still need to do your due diligence and be selective. The bottomline is, you need to go beyond the cut rating and use tangible data like the ASET or Idealscope images to help you make the final selection.
To give you some perspective of what defines a “perfect” cut diamond, watch the following videos to see how a well-cut diamond looks like in real life. Feel free to click on the respective links below to view full details of each diamond.
Most AGS ideal cut diamonds have strong light return and great scintillation. Both diamonds below receive the best cut grading of 000 from AGS and I want you to look at them to see if you can spot differences between them.
The diamond on the left is one that is cut with superb precision and performance. This is a textbook example of an ideal cut diamond I would buy. In fact, you can see the distinct arrows patterning in the video listing.
On the other hand, the diamond on the right is a terrible choice. The ASET in the grading report shows mediocre contrast patterning and light leakage. Even though this diamond has the same exact AGS 000 grade, it pales in comparison to the other stone.
The GIA triple excellent cut range of diamonds is a mixed bag. You will mostly find mediocre diamonds and will rarely be able to find one that has top-notch light return and cut precision.
FYI, in order to find a single GIA diamond that has great light return and cut precision, I had to dig through hundreds of GIA 3Ex diamonds to cherry pick the diamond on the left.
As for the other diamond, it’s the typical stuff you will find in the GIA excellent cut range and you can probably tell that it is poorly cut.
The GIA Very Good cut grade consists of diamonds that have issues with brightness, scintillation and finish. For the record, I will NOT recommend buying any diamonds in this cut grade.
In this category of diamonds, you can expect to see poor performance and increased darkness in the diamonds. You will also start to see more diamonds with splintery patterning and poor weight-to-size ratios.
As you can see from the images above, the very good cut diamond on the left displays decent optical symmetry but don’t let this fool you. It doesn’t necessarily mean it will look more brilliant than another diamond with poor optical symmetry.
The bottom-line here is that the brightness and brilliance of a diamond are very much dependent on facet proportions and not so much on its optical symmetry.
Really, there’s nothing good about the GIA Good cut rating. You should never consider buying diamonds within this cut grade unless you want your diamond to look like frozen spit.
Most diamonds are cut with excessively steep crown angles and/or shallow pavilions because the cutter wants to maximize weight retention for more profits. As a result, many diamonds with Good cut ratings have problems like nail heads and fish eyes.
The diamonds in this range are lackluster and have poor brilliance. Sadly, a huge percentage of round diamonds in the current market falls into this range of quality.
This is the bottom of the barrel when it comes to diamond cut quality. Fair and Poor cut diamonds usually have steep crowns and steep pavilion angles which gives them a really dark looking appearance. This makes them look extremely small for their carat weight.
Because of their abysmal proportions, their brilliance and sparkle are horribly affected. Avoid fair and poor cut diamonds like the plague!
If you want to buy a lively and sparkly engagement ring, you should avoid diamonds with a Very Good cut grade or below.
As a consumer, you also need to understand that even if 2 diamonds have the same cut rating on paper, they can have completely different appearances. Using the two AGS ideal cut diamonds (triple 000) as examples, you can clearly see that one has a more consistent contrast patterning over the other.
Likewise, you can also see a similar phenomenon within the GIA cut grades. The reason behind this is that within each grade, some degree of variations is allowed as long as they are within the cut rating’s tolerance.
And as I said earlier, the GIA excellent cut grade is very broad. If you want to separate the wheat from the chaff, you need to use cut performance data to analyze the diamonds.
Vendors like White Flash, Brian Gavin and James Allen are some of the best vendors to shop for engagement rings because of their high quality diamonds and the amount of tangible information they provide in their listings.
Besides cut proportions, there are also other factors that can affect a diamond’s cut grading and overall appearance. I will go into more details on the next page.