What is the GIA?
“I’m shopping for a diamond and keep running across references to the GIA. I understand that the GIA is a gemological laboratory, but it seems like it’s more than that. I get the impression that the GIA also trains people to be gemologists. But it also seems like a research laboratory and perhaps a governing body within the industry? What exactly is the GIA? And if you don’t mind me asking, why aren’t Brian Gavin Signature diamonds GIA Certified? It seems like every BGD Signature diamond I look at is graded by the AGS. What are the differences between the AGS and the GIA in terms of accuracy?”
The GIA Gem Trade Laboratory:
The little known formal name for the GIA, is the Gemological Institute of America Gem Trade Laboratory (GIA-GTL). That happens to be quite a mouthful, so you can imagine why people simply refer to it as the GIA.
The GIA was created in the 1950’s by Robert M. Shipley, who at the time was a veteran of the diamond and jewelry industry. The concept was to create a unified system to describe diamond characteristics (Carat weight, Color, Clarity, Cut quality) and the inclusions within a diamond. This would enable professionals within the diamond industry to describe diamonds in uniform fashion.
The obvious benefit to this is that a diamond dealer in New York City can have a reasonable idea of what a diamond dealer in Antwerp, Belgium is referring to when he describes a three grain, 3X RBCD as being F-color and VS-2 in clarity with a feather on the edge of the table, crossing into the star, and a few pinpoints in the upper bezel.
Diamond Speak, It’s All Greek?
Now if all of that seemed like psycho-babble, that’s because industry jargon is intended to be, well, industry jargon. It’s intended to be used by industry professionals, but that doesn’t mean that it’s difficult to understand. You simply need the code to break it down and translate it into simple English.
What the dealer is actually describing is a 0.75 carat (three grains, each grain representing a quarter carat), GIA Excellent cut (3x), round brilliant cut diamond (RBCD) that is F-color (within the D-E-F colorless range) and VS-2 in clarity (very slightly included, faces-up eye clean) with a feather (minute fracture) that is located on the edge of the table facet (largest facet on top of the diamond) and crossing into the triangular shaped star facet.
There is also a few, very small (minute) pinpoint size diamond crystals located within the kite shaped bezel facets that border the table facet. All in all, that sounds like a really nice VS-2 clarity diamond. I can picture the inclusions without seeing them. But what about the proportions?
Is GIA Excellent good enough?
People tend to assume that a diamond is going to look exceptional, simply because it has an overall cut grade of GIA Excellent. Unfortunately, that is not necessarily the case.
The reality is that the GIA Excellent cut grade encompasses a range of proportions, which is rather broad by our standards. As with every range or spectrum, there is a low-end, a mid-range, and a high-side. What is important to realize is that when it comes to diamond proportions, you want to focus on the mid-range, which is also known as the target zone.
The challenge with the GIA grading platform (from our perspective) is that they round off several of the measurements reflected on the diamond grading report to the nearest half a degree, or half a percent.
This means that a crown angle of 34.3 degrees is going to be rounded up to 34.5 degrees. While a crown angle of 34.7 degrees is going to be rounded down to 34.5 degrees. While this is probably not an issue, since both the high and low range reflected here, represents the mid-range for crown angle, it can be a problem with steeper or shallower crown angle measurements.
Why? Because the crown angle of a diamond dictates the balance of brilliance (white sparkle) and dispersion (colored sparkle). A crown angle in the mid-range of the spectrum is likely to produce a virtual balance of brilliance and dispersion. But tilt the measurements to one side of the spectrum or the other, and you’re likely to throw off the balance of sparkle factor.
So how does this affect light performance?
While the crown angle measurement is primarily going to affect the balance of brilliance and dispersion, the pavilion measurements will have a dramatic effect upon the volume of light return.
Brian Gavin is a fifth generation diamond cutter, with a passion for creating diamonds that exhibit incredible light performance. So, he knows the importance of cutting each section of the diamond to create the highest volume of light return, while maintaining a balance of brilliance and dispersion.
But most cutters are focused on cutting diamonds to maximize the retention of carat weight, because that is how you maximize the profits from each piece of rough. This is why you’ll often see GIA Excellent cut diamonds with pavilion angles steeper than 41.0 degrees, combined with a pavilion depth of 43.5% which happens to be the kiss of death from our perspective.
How the GIA could provide better peace of mind:
We want to be clear by saying that our experience using the GIA Gem Trade Laboratory has been excellent. We find their grading accurate and consistent for carat weight, clarity, color, fluorescence, polish and symmetry. However, we feel that they fall short on cut quality, as compared with the AGS Laboratory.
This is because of the manner in which they round off the measurements of the diamond, and because they don’t take light performance into account. Whereas, the AGS Laboratory reports the actual measurements of the diamond (based upon the average of eight measurements per section) and the AGS uses Angular Spectrum Evaluation Technology (ASET) to judge the degree of light performance.
While not entirely conclusive, the Light Performance based grading platform offered by the AGS Laboratory is, well, light years ahead of the GIA-GTL at this point. Brian Gavin Signature diamonds are submitted to the AGSL for grading, because we feel they offer the most state-of-the-art assessment available at this time.
But it could be better, which is why we supplement their report, and provide additional images of the diamond as seen through a Hearts & Arrows scope, and an Ideal Scope. We also provide our own ASET scope image of the diamond, to support the findings of the AGS. In short, we strive to provide you with the most accurate insight possible.