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 numerical 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 in 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.
Although both GIA and AGS might use a slightly different system for grading diamond cut, one thing is ubiquitous. The overall optical performance a diamond displays is a key component in determining its cut grade. Without getting into 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 by purchasing simulants then spending money on a diamond that doesn’t sparkle well.
Very Good: Average
Disclaimer: This is just a representation of my personal views because I value cut above anything else. Even for diamonds with ideal/excellent ratings, I would always take extra steps to select the best possible choice.
AGS Ideal (0)
0.70 Carat H – SI1 AGS Ideal Cut Round Diamond
0.61 Carat I-VVS2 AGS Ideal Cut Round Diamond
As you can see from the images above, the very good cut diamond on the left has nice optical symmetry (arrows patterning). However, this 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 is very much dependent on facet proportions and not so much on its optical symmetry.
Whoa! What had happened here?
Sadly, a huge percentage of round diamonds in the current market falls into this range of quality.
It is also interesting to note that there can be differences in appearances even if 2 diamonds share the same cut rating. Using the two AGS ideal cut diamonds (triple 0’s) as examples, you can clearly see one has a more consistent arrows patterning over the other. The reason behind this is that within each grade, some degree of variations is allowed as long as they are within a specific tolerance.
Besides proportions, there are several other factors which can affect a diamond’s cut grading. I will go into more details on the next page.