When it comes to diamond qualities, it is often the case that small increases or decreases in quality (from example, moving from an H to an I color diamond) are not immediately noticeable, or indeed, noticeable at all for many buyers. In this way, making small compromises with technical diamond grades can be the perfect way to balance your budget and still end up with a beautiful diamond.

But the CUT quality of a diamond, specifically the GIA cut grade, does not follow this same pattern. Many customers ask us if there is a tangible difference in the Very Good VS Excellent cut grades – the answer is a resounding YES.

Cut grades are much, much more than notes on a piece of paperwork. Cut quality determines the light performance of the diamond and the amount of fire and brilliance it will deliver. You will notice a BIG difference between a top GIA excellent cut and a GIA very good cut.

Cut quality unleashes four, key optical properties in a diamond:

Brilliance – Brilliance in the internal and external reflections of white light. It can be thought of as ‘brightness’.

Fire – When white light is refracted, it can create rainbow of colored flashes – this is diamond fire.

Pattern – Pattern is the equal, balanced display of light and dark areas – hearts and arrows patterning is the ultimate example of a precise facet pattern.

Scintillation – A contrast of black and white which results in a twinkling/sparkling effect -these sparkles should be active and uniform.

Overall cut quality, polish, and symmetry are each given a grade; when you hear a diamond described as a ‘triple ex diamond’ it means it has received an excellent grade in all of these categories. *Note: GIA currently only grades overall cut on round brilliant diamonds.

There is room for preference when it comes to certain diamond qualities; we see many customers who move away from the icy white tone of a colorless diamond, expressing a genuine preference for the warmer tones of diamonds with a lower color grade. This also saves them money! When it comes to cut quality, it’s fairly objective; diamonds with a top-quality cut look and perform better than those with a lower cut grade, and this is obvious even to non-expert observers.

Analyzing cut quality is as complex as it is fascinating; our guide to analyzing cut quality goes into great detail and is perfect for those looking to build on their diamond knowledge and understand more about this crucial aspect of diamond quality.

Excellent is the top cut grade that the GIA offers for overall cut quality. Unfortunately, this category is overly broad. Buyers may assume that any diamond graded Excellent will have a phenomenal cut; while this is a logical assumption, it is simply not the case. Around 55% of GIA diamonds on the market carry an excellent grade – of these, very few reach the exacting proportions needed to unleash the full potential of a diamond. As much as 30% of these excellent grade diamonds would not be recommended by experts.

The GIA and AGS are two top tier labs and were founded by the same group of jewelry professionals. Although the standards for color and clarity are consistent between the two labs, there is a big difference when it comes to cut quality. The AGS invested in critical analysis of cut quality, filling a void in the market to provide a stricter evaluation of this crucial factor, and offered a cut quality report ten years before GIA did. The GIA eventually followed suit, but created a very forgiving system that made the majority of diamonds on the market look good on paper. AGS on the other hand, continues to be the industry leader with their rigorous scientific light performance cut grading. You can read more about how the GIA and AGS labs compare, and uncover why we use the AGS for our A CUT ABOVE® super-ideal cut diamonds.

The images above show the ASET, Idealscope and Hearts and Arrows view of a 3.36ct D-VS1 round brilliant diamond. This diamond received a GIA cut grade of excellent, but as the advance diamond imaging shows, there are some obvious problems with the cut quality.

You can plainly see areas of light leakage and obstruction. Several of the hearts are imperfectly formed indicating a lack of optical precision. And the ASET also shows intentional “digging out” (green facets) around the girdle – a technique used to correct problems, but at the expense of edge-to-edge brightness. We analysed this diamond as a contender for our Premium Select diamonds– it did not make the cut. The advantage of diamond imaging is that you can see for yourself how a diamond is performing – it shows the importance of going beyond the grade on a certificate. We reject the majority of GIA excellent cut diamonds we evaluate due to improper proportions, poor optical precision, and compromised light performance.

This is not to say the GIA cut grades are intentionally deceptive. It is simply that their cut categories are so broad as to be of little value to the discriminating shopper looking for diamonds with the very best sparkle factors. The AGS system is more precise, and thus it is easier to find a quality cut using the AGS grades, particularly diamonds carrying their Ideal grade.

Given the GIA Excellent grade is overly broad, diamonds falling into their next lower grade -Very Good cut - fall considerably further from the goal of delivering outstanding optical performance. You will notice a drastic difference in light performance and overall beauty when you compare a top tier diamond with a diamond carrying a very good cut grade. Remember that both excellent and very good cut boundaries cover a range of proportions – this means that there is an upper end and a lower end to both categories. So the distance between a top Excellent cut and a bottom Very Good, involves an extremely large range, with significant implications for diamond beauty. It may not be ‘night and day’ but it is “dusk and noon”!

Take for example the following diamond graded by GIA in 2016 as a Very Good cut. The proportions are way out of the range of what most people would call ‘very good” with an extremely steep crown angle and a depth percentage that is so high that the diamond will appear very small for its weight. In fact the diamond weighs .97ct and has a diameter closer to that of a well cut .75ct! And as the light performance images dramatically illustrate, light is leaking badly (pouring really!) through the bottom of the stone all around the center of the diamond. As for optical symmetry, the hearts and arrows patterns reveal obvious problems with faceting precision.

For excellent cut diamonds, the first task is finding a diamond with proper proportions. Further refining the choice will require advanced diamond imaging to find a true winner. When it comes to GIA very good cut diamonds, it is still possible to find a pleasant stone, but the search will be much more challenging and will require closer scrutiny.

Choosing a diamond with a GIA report is an excellent place to start. We offer our customers further assurances on cut quality by giving expert scrutiny to all GIA diamonds for our Premium Select category. These in-stock diamonds have been fully vetted and imaged, ensuring the best proportions, optical symmetry, and light performance available in a GIA diamond. Premium Select diamonds also include our very popular Lifetime 100% Trade-up benefit.

If you are shopping for a round brilliant diamond with a GIA grading report, and want to ensure you get a diamond with the maximum sparkle factor, we have done all the work for you! We invite you to contact us and speak to one of our knowledgeable and friendly GIA accredited diamond consultants who will be happy to guide you in your search.