“I’m wondering whether you can shed some light on the differences between AGS Ideal vs GIA Excellent cut diamonds. All of the jewelry stores in my area, seem to only offer diamonds graded by the GIA, IGI, or EGL, and only one seemed to be familiar with the AGS Laboratory. From what I’ve read online, it looks like the AGS & GIA are the most widely recognized. However, it appears to me that the AGS provides more detail regarding light performance.
By the way, I’m looking for a hearts and arrows cut diamond, weighing between 1.20 – 1.49 carats. My girlfriend is a professional photographer, so she tends to be really good at judging diamond color. In view of that, I think that something in the F-G color range will be perfect for her. We definitely want the diamond to be eye clean, so probably something in the VS-2 to VS-1 clarity range.”
GIA vs AGS, which gemological laboratory is best?
The GIA Laboratory definitely seems to be the most recognized gemological laboratory in the world. This is probably because they’ve been around the longest, thus they benefit from worldwide recognition. However, when it comes to recognition within the realm of super ideal cut diamonds, the King of the Hill is definitely the American Gem Society Laboratory (AGSL).
While the GIA Laboratory has been around longer, the AGS Laboratory introduced the concept of an overall cut grade first. The GIA and AGS are actually sister organizations of sorts, both being started in the 1950’s by Robert M. Shipley.
He created the Gemological Institute of America (GIA) in the hopes of creating a systematic method of describing diamond characteristics and quality, which could be used by diamond dealers around the world. The GIA Gem Trade Laboratory (GIA-GTL) was launched a short time later, and provided diamond dealers with a standardized report which reflects the characteristics at the time the diamond is graded.
The American Gem Society (AGS) is a membership organization, which promotes a foundation of morals and ethics for industry members to adhere to. In the late 1990’s former GIA Lab Director, Peter Yantzer, left the GIA to open the American Gem Society Laboratory. Because he wanted to provide consumers with a more in-depth analysis of the diamonds they were buying.
The Differences between AGS Ideal vs GIA Excellent cut diamonds:
At the time, the GIA was not providing people with the crown and pavilion measurements for round brilliant cut diamonds. They were only revealing the total depth and table diameter measurements. Peter Yantzer wanted to create a report that revealed the crown angle, crown height, pavilion angle, and pavilion depth measurements.
The majority of diamond dealers were against this information being published, because doing so would make it possible for people to better understand light performance. The reality is that the vast majority of diamonds you’ll find out there are sub-par by our standards for cut quality.
Which is why Brian Gavin jumped at the chance to submit his diamonds to the AGS Laboratory for grading! Finally, there was a gemological laboratory that made it possible to show our clients just how amazing Brian Gavin Signature diamonds are cut!
Imagine how excited we were when the AGS Laboratory introduced their Light Performance grading platform in June of 2005! Interestingly enough, it was only then that the GIA-GTL finally decided to add the crown and pavilion measurements to the diamond grading report for round diamonds. They still don’t provide those measurements for fancy shape diamonds.
And only the AGS Laboratory uses Angular Spectrum Evaluation Technology (ASET) to measure the brightness of diamonds. That is the multi-colored, red, green, and blue, image of a diamond that you’ll see on the diamond grading report for every Brian Gavin Signature diamond.
Take a look at how consistent the pattern of light reflecting throughout this 1.231 carat, G-color, VVS-2 clarity, Black by Brian Gavin diamond appears in the ASET image provided on the diamond grading report. Unlike the static ASET images that we also provide, this image is comprised of data obtained while the AGSL scanned the diamond using ASET, while it was in rotation. This provides a more in-depth Light Performance analysis, that you can really see!
How the AGS & GIA report proportions differently:
The AGS Ideal and GIA Excellent diamond grading reports that appear at the top of this article, are for the same Brian Gavin Signature diamond. We submitted the diamond to the AGS Laboratory for grading, and then submitted it to the GIA Gem Trade Laboratory. As you can see, both laboratories gave the diamond the same carat weight, color, clarity, and overall cut grade of AGS Ideal / GIA Excellent cut.
The proportions of the diamond are expressed slightly differently, and this is one of the differences between the two gemological laboratories. Both laboratories determine the proportions, by taking eight individual measurements per section. Then the computerized proportions analysis software, adds those measurements up, and then divides that number by 8 to determine the average.
The AGSL then publishes that average number on their diamond grading report. Thus, if the average of the eight crown angle measurements is 34.8 degrees, that is what you’ll see on the AGS diamond grading report.
However, the GIA then rounds that number off to the nearest half a degree for crown angle. Thus, a diamond with a crown angle of 34.8 degrees, will be rounded off to 35.0 degrees on a GIA diamond grading report. That’s probably fine, but a crown angle of 35.2 degrees will also be rounded off to 35.0 degrees.
The GIA also rounds off the crown height measurement to the nearest half a percent. Same with the pavilion depth, which is also rounded off to the nearest half a percent. And the lower girdle facet length? Well, that’s rounded off to the nearest 5%. Read that last sentence again, and just let that sink in. You can imagine how much wiggle room this practice provides the producers of GIA Excellent cut diamonds.
Brian Gavin Signature Diamonds are Graded by the AGS Laboratory:
Now you can clearly see, why Brian Gavin prefers the Light Performance grading platform of the AGS Laboratory. Only the AGS Laboratory gives you the insight provided by their proprietary Angular Spectrum Evaluation Technology (ASET). And even if somebody provides you with a picture of a GIA Excellent cut diamond as seen through an ASET Scope, that’s only showing you how the diamond looks from the static 90 degree vantage point.
While the ASET image provided on an AGS Diamond Quality Document, is based upon a compilation of data obtained while the diamond was being scanned from multiple vantage points. Plus, the AGSL is not further rounding off the measurements of the diamond, after determining the averages.
It just seems to us, that the insight provided by the Light Performance grading platform of the AGS Laboratory, provides you with a better perspective of our diamonds. Enabling you to see that they are better, beyond a shadow of a doubt.
This is not to say that the AGS Laboratory is better than the GIA Gem Trade Laboratory. You can clearly see from the diamond grading reports pictured above, that they grade comparably for diamond carat weight, clarity, color, polish, and symmetry. Although they use different terms to describe the overall cut grade, culet size, and degree of fluorescence.
Perhaps the GIA-GTL will introduce some sort of light performance grading platform in the future, but for the moment, the AGS Laboratory appears to be light years ahead of the competition. The same could be said about Brian Gavin Diamonds, which is why we also provide you with images of our diamonds as seen through Hearts & Arrows, and Ideal Scope images, and a variety of lighting environments.
The imaging technology to produce these images is readily available and reasonably priced, so why don’t all diamond dealers online provide you with this sort of insight? Why don’t they send their diamonds to the AGS Laboratory for grading, when the insight provided by the Light Performance grading platform would make it easier for you to see how light is reflecting through their diamonds, and show you the degree to which those diamonds are leaking light? That is a much more interesting concept than AGS Ideal vs GIA Excellent cut diamonds 😉