A Visual Look At The Different Types of Diamond Cut Grades

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.

history of gia

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.

Various Categories of Cut Grades For Round Diamonds

 
  • Ideal (For AGS)
  • Excellent
  • Very Good
  • Good
  • Fair
  • Poor
 

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.

Here Are My Own Interpretation About the Different Gradings

 
Ideal/Excellent: Not All Are Good

Very Good: Average

Good: Bad

Fair: Vile

Poor: Worthless


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.

Sample Pictures of Round Diamonds From the Various Cut Grades

Special thanks to James Allen for providing the photographs here for educational reference.

AGS Ideal (0)

0.70 Carat H – SI1 AGS Ideal Cut Round Diamond
0.61 Carat I-VVS2 AGS Ideal Cut Round Diamond

ags triple 0s


Excellent Cut

different cut grades in diamonds


very good cut round brilliants
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.


Good Cut

 
good cut is not enough!
poor definition of features
 

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.


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12 Comments

  1. Janet R.-
    June 16, 2013 at 1:35 am

    I have a question about the FacetWare program. I bought a GIA graded diamond and have the Dossier report on hand. I’m sure I plugged in the values into the software correctly and it returned an Excellent grading.

    However, on my report, the cut grade is listed as Very Good. Do you know why?

    Janet

  2. Paul Gian-
    June 20, 2013 at 3:40 am

    To the best of my knowledge, the FacetWare program uses the same system and algorithm that real life lab graders use when examining a stone.

    Do note that the entire grading process of a round diamond consists of a few parts.

    1) Observation of the diamond under 2 different lighting for fire, pattern and brightness.
    2) Proportions based grading (table %, depth % etc…).
    3) Symmetry and polish ratings.

    The FacetWare program covers only one aspect (2) of the inspection process. If your diamond takes hit in any factors that lie in (1) or (3), the cut grade is downgraded.

  3. Janet R.-
    June 20, 2013 at 3:48 pm

    The Dossier report lists both polish and symmetry ratings as Excellent. In this case, it is the observational process that causes the diamond to be graded as a Very Good?

  4. Paul Gian-
    June 20, 2013 at 7:02 pm

    Yes. I am very sure that this is the case.

  5. joanne-
    September 17, 2015 at 12:29 pm

    I found a stone that has Excellent polish and Excellent symmetry but the cut is just Good. If the symmetry is Excellent I dont understand why the Good rating for the cut. The diamond is lovely though with a G color. Please explain.

  6. Paul Gian-
    September 19, 2015 at 3:02 pm

    Polish and symmetry grades are only part of the equation. GIA looks into a diamond’s proportions as well as a physical examination of the diamond under various lighting conditions for sparkle, patterning and scintillation. The stone you were looking at failed terribly at one or more of these aspects.

  7. Paul Gian-
    November 24, 2015 at 6:30 am

    Depends on what you are really after.

    For a diamond with pinfire flashes of light return, this would be the best option: https://www.jamesallen.com/loose-diamonds/cushion-cut/1.81-carat-h-color-vs2-clarity-sku-658574

    For a different flavor of sparkle/scintillation, this would be the best option for light performance: https://www.jamesallen.com/loose-diamonds/cushion-cut/2.00-carat-h-color-vs1-clarity-sku-597854

  8. Jay-
    November 24, 2015 at 6:47 am

    Thank you for the prompt reply. Which one would be the best bang for the buck? How about cut? Light performance (outside of the 2.0 carat)?

  9. Paul Gian-
    November 25, 2015 at 7:48 am

    As I mentioned earlier, the light performance of these 2 diamonds differ in their characteristics. Both diamonds have good optics for the type of sparkle they offer. I personally gravitate towards this diamond: https://www.jamesallen.com/loose-diamonds/cushion-cut/2.00-carat-h-color-vs1-clarity-sku-597854 because I like its scintillation pattern more.

  10. Germanium-
    July 4, 2017 at 6:53 pm

    Hi Paul,

    I am shopping for a Cushion shaped yellow diamond and I was wondering if the non-round diamond cut follows the same principle as the round ones?

    I was also browsing the Leibish website and reading the GIA reports but it seems that a few things are missing for the Cushion diamonds compared to the round ones.

  11. Paul Gian-
    July 5, 2017 at 2:09 am

    With yellow diamonds, the selection process is completely different for colorless diamonds (even if you are choosing a round canary stone). This is because color is the more important factor and with colored diamonds, the way to analyze cut quality is different from non colored stones. Colored diamond GIA reports do not have cut grades and that’s normal.

    Colorless diamonds – light performance and sparkle is key.
    Colored diamonds – the way the diamond is cut needs to reinforce color and are generally cut deeper. This is true for cushion shaped yellow diamonds.

    I actually bought one canary diamond ring for my wife recently: http://beyond4cs.com/2016/08/cushion-cut-fancy-intense-yellow-diamond-engagement-ring/

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