Did GIA Solve Two Problems with AGS Technology?

[Texas Leaguer]

The Ideal cut grade was brought to the forefront of diamond quality grading in the modern age by the American Gem Society (AGS) in the mid 1990’s. It was at this time that the AGS established the American Gem Society Laboratories (AGSL), with a strong emphasis on cut quality analysis. In 2005 AGSL released their groundbreaking light performance grading system using advanced light ray tracing and for the first time provided an accurate, consistent and repeatable scientific cut grade system for diamonds. In the same year GIA released its first cut grade system for round diamonds; one that is parameter-based and relatively broad and forgiving. In 2022 GIA acquired the light performance grading technology from AGS and now provides AGS Ideal addendum reports on qualifying diamond sent in for a GIA report. The clear implication is that GIA recognizes its own top grade of Excellent to be overly broad, and now provides a means for shoppers to separate the truly excellent cuts from the rest of the diamonds in the Excellent category. Another even bigger implication pertains to the future of fancy shape cut grading.

Key Takeaways:

• GIA Excellent is a broad and forgiving grade range.
• AGS Ideal light performance grading is much more rigorous
• GIA acquired AGS technology in 2022
• GIA now offers an AGS Ideal addendum reports on rounds and fancy shapes
• AGS Ideal with proven optical precision is known as Super Ideal
• GIA is likely to roll out fancy shape cut grading using AGS technology

Surveys have been done on the diamonds listed on the most popular international diamond databases and have found a strong majority of the rounds listed were awarded the Excellent cut grade from GIA. This fact alone suggests that the Excellent grade is not rigorous enough to enable shoppers to identify the exceptional cuts. With GIA now able to provide an Ideal report, that problem is largely solved.



GIA rolled out the AGS Ideal addendum report shortly after the acquisition of the technology, signaling that the AGS light performance grading system would be the way forward for GIA in this vital area of diamond grading. Because the technology is also applicable to fancy shape diamonds, and because cut quality of fancy shapes is the new frontier in diamond grading, it is reasonable to assume we will eventually see GIA rolling out the system more broadly.

Currently the only overall cut grade provided on a GIA report is for the standard round brilliant. However, qualifying fancy shape diamonds are also eligible for the AGS Ideal addendum report. This further suggests that GIA intends to use the AGS system as it rolls out fancy shape cut grading more broadly. At the present time, only those diamonds (rounds and fancies) that pass the AGS ray tracer as Ideal (AGS 0) are eligible for an addendum report. That is, GIA is not issuing cut grades of AGS1 or lower on any diamonds at this time.

GIA Excellent Cut is Demonstrably Broad
A straightforward way to see how broad GIA Ex is compared to AGS Ideal is to look at their respective parametric grading charts. While the AGS system is light performance based and does not rely on charts, the charts provide some guidance on potential candidates for the top grade based upon averaged parameters. The AGS Ideal candidates are colored in red below while the much broader area outlined in black are potential GIA Ex candidates. You can also see the range of probable AGS grades contained within the GIA Ex range – down to AGS 5 on the 0-10 AGS scale where zero is Ideal.




Light Performance Imaging Reveals Deficiencies
Using advanced light performance imaging it is easy to see that GIA Excellent cut diamonds at the margins have deficiencies such as light leakage, too little or too much contrast, painting and digging, and other failings that can result in significantly diminished performance. The following two GIA EX diamonds illustrate a range of deficiencies contained with the grade.

GIA EX with lack of precision and painting



GIA EX with light leakage and dug out upper girdle facets​

GIA Report with AGS Ideal Addendum
As long as AGS Laboratories was in operation and as well respected as their cut grading is, there was always lingering uncertainty in some corners of the market that their color and clarity grading was fully on par with GIA. In many cases shoppers would feel compelled to invest in both reports, and in cases where normal deviation occurred between them, consumer confusion would result. Today, that dilemma has been solved. In a “best of both worlds” development shoppers can now find GIA reports with AGS Ideal light performance addendum reports. The submitting client can now request the addendum report on any qualifying diamond that is sent to GIA for a grading. The cut grade does not appear on the GIA report, but is crossed referenced in a separate AGS Ideal addendum report. The addendum also includes an ASET light map of the diamond. The grading report and addendum can both be accessed on the GIA Report Check website.

​

A GIA diamond with AGS Ideal addendum is assurance that the cut quality is at the top of the scale, or to say it another way, right in the heart of the GIA Excellent range - not at the periphery where demonstrable light performance issues exist in the GIA parametric grading structure.

The Super Ideal – An Island within the GIA Ex Ocean
We have seen how the AGS Ideal grade is a narrow subset of GIA Ex, demonstrating that the GIA Ex grade is much broader and contains diamonds with demonstrable light performance issues. But there is a further subset of the best AGS Ideal cuts that creates an even more dramatic illustration of how broad the GIA Ex grade is compared to the very best precision cutting.

The main difference between an AGS Ideal and a bona fide Super Ideal, is in 3D precision (aka optical precision or optical symmetry). This is not something that AGS grades for, but makes a difference in terms of craftsmanship and optimization of of the facet design. A true super ideal should be accompanied by the light performance images that conclusively document the level of precision, such as ASET, IdealScope and Hearts and Arrows images.

An AGS Ideal with imperfect optical precision (not super ideal)
​

Super Ideal – AGS Ideal with perfect optical precision​

AGS Ideal – 3D Analysis
The AGS light performance system uses an accurate 3D scan to create a model of the diamond and all the facets including angles and pointing directions (azimuth). This is run through a computer ray tracing program that illuminates the model with 30,000 virtual light rays and measures brightness, contrast, dispersion (fire), and light leakage. A grading structure is then built for each shape based upon the characteristics found in the very best specimens of each shape.

While making decisions about what constitutes the best specimen requires some subjectivity, GIA has world-class ability to do extensive observational surveys and to make statistically valid determinations.

The Future of Fancy Shape Cut Grading
The biggest void in diamond grading today is cut grading of fancy shapes. Because light performance is the sum contribution of all facets in three dimensions, and because non-round shapes have more parameters at play (including but not limited to length/width ratio), they are more complex by definition. And because many, if not most, fancy shapes have multiple variations or modifications, the level of complexity quickly reaches a point where ray tracing is the only feasible method for measuring and grading cut quality. GIA now has that capability, and with their reach and reputation, a unique opportunity to vault to the lead of the fancy shape cut grading space.

Conclusion
GIA invented the diamond grading system in the mid twentieth century and have earned the best reputation and greatest reach of any gem laboratory for accuracy and consistency. They were slow to move into the cut grading space in a major way and were very conservative in rolling out their cut grade system for round diamonds, structuring their top grade of Excellent in an overly broad manner. But with the acquisition of AGS light performance technology they have now created a subset of the best in the GIA EX category by issuing the AGS Ideal addendum reports on those diamonds which qualify. And more importantly, they now have the foundation with which to not only compete, but to dominate in the fancy shape cut grading space.

The acquisition and implementation of AGS light performance technology solves two problems for GIA, and in time may be seen as one of the most brilliant innovations in GIA’s long and storied history.

FAQs
Is a diamond with a GIA Ex cut grade the best you can get?
Not necessarily. The GIA Ex cut grade is very broad, containing many diamonds at the margins with appreciable light performance deficits. The AGS Ideal grade is a more rigorous standard.

How do I get an AGS Ideal report?
The AGS Laboratories was closed in 2022 when GIA acquired the lab, its cut team, and its technologies. There are still some diamonds in the market have full AGS reports from before that time, but GIA now provides an AGS Ideal addendum report on qualifying diamonds.

Does GIA provide AGS Ideal reports on fancy shape diamonds like oval and emerald cut?
Yes they do, and other non-round shapes as well. But they are hard to find in the market at the present time.

What is a Super Ideal cut diamond?
A super ideal is a diamond that has a cut grade of AGS Ideal and also has proven optical precision including true hearts and arrows patterning.

When will GIA start putting overall cut grade on fancy shape diamonds?
It is hard to say when that will happen, but there is good reason to believe it will be coming. With the acquisition of AGS light performance technology, GIA now has the foundation to provide accurate and consistent scientifically vetted light performance cut grades on all shapes.


What are your thoughts on the AGS Ideal addendum report? Were you aware that fancy shape diamonds are eligible? What do you think this means for the future of cut grading and the value of a GIA report?

Please share your thoughts below.

 

[MissGotRocks]

I love the AGS addendum report but not as much as I loved AGS! The GIA rounding leaves a lot to be desired. I had initially thought that the addendum would also include angles, so was dismayed to see that it was limited. I guess GIA doesn't want to be any more exacting than they currently are as the triple excellent cuts would go way down in number. It also seems that the GIA has no real competition in terms of grading - they are the gold standard and now with AGS gone there is no one else on par. You can't even double check the color/clarity of diamonds with anyone else. I honestly never thought that GIA acquiring AGS would be a boon for diamond enthusiasts. Too much like a monopoly for me - competition can result in more transparency and honesty. Having said all of that though, I am glad that the AGS addendum exists. Just an added layer of assurance - particularly if you were dealing with a jeweler or company that wasn't that well versed in cut quality.

 

[Texas Leaguer]

I love the AGS addendum report but not as much as I loved AGS! The GIA rounding leaves a lot to be desired. I had initially thought that the addendum would also include angles, so was dismayed to see that it was limited. I guess GIA doesn't want to be any more exacting than they currently are as the triple excellent cuts would go way down in number. It also seems that the GIA has no real competition in terms of grading - they are the gold standard and now with AGS gone there is no one else on par. You can't even double check the color/clarity of diamonds with anyone else. I honestly never thought that GIA acquiring AGS would be a boon for diamond enthusiasts. Too much like a monopoly for me - competition can result in more transparency and honesty. Having said all of that though, I am glad that the AGS addendum exists. Just an added layer of assurance - particularly if you were dealing with a jeweler or company that wasn't that well versed in cut quality.

Insightful comments MissGR!
GIA has a huge and diverse constituency that they have to carefully consider in anything they do. Hence, they are slow moving and conservative. But adopting AGS cut grading, and immediately implementing it, is a good sign. It will be interesting to see what they do with it over the next months and years. I think it could be a game changer.

 

[MissGotRocks]

Insightful comments MissGR!
GIA has a huge and diverse constituency that they have to carefully consider in anything they do. Hence, they are slow moving and conservative. But adopting AGS cut grading, and immediately implementing it, is a good sign. It will be interesting to see what they do with it over the next months and years. I think it could be a game changer.

You have always seemed optimistic about this and I hope you are right. Would love to see GIA expand on this sooner rather than later. Fancy cut grading would be challenging, yet welcome, for many consumers.

 

[Tonks]

The GIA rounding leaves a lot to be desired. I had initially thought that the addendum would also include angles, so was dismayed to see that it was limited.

Agree—I too wanted all the angles, not the rounded numbers. Whiteflash has helped there by running Sarin scans on both diamonds I have purchased with the new reports. @Texas Leaguer
I really appreciate that!

 

[Texas Leaguer]

Agree—I too wanted all the angles, not the rounded numbers. Whiteflash has helped there by running Sarin scans on both diamonds I have purchased with the new reports. @Texas Leaguer
I really appreciate that!

Thank you @Tonks.
One of the many advantages of having in-house diamonds is the ability to provide additional information and services.

 

[Texas Leaguer]

You have always seemed optimistic about this and I hope you are right. Would love to see GIA expand on this sooner rather than later. Fancy cut grading would be challenging, yet welcome, for many consumers.

Yes. Optimisitic about the eventual outcome. But not necessarily about the timeline!

 

[oldminer]

My feeling is that Super Ideal cuts have added value along with some added costs applied. AGS standard Ideal cuts have some added value an somewhat less added costs. Both kinds of Ideal cuts have the interest of a particular market at the retail level which hungers for "the best" and who can afford levels of luxury in their buying.

A far larger part of the diamonds market wants reasonably well cut, sparkly diamonds at a price that fits their ability and budget. This is the large market territory covered by GIA XXX to GIA VG.

Having sold many OEC and OM diamonds as well as all sorts of modern diamonds for 40+ years, I found personal pleasure in allowing retail stores and their customers to make diverse choices. There is no reason that round diamonds all must handle light and symmetry in a virtually identical manner. Consumers can handle making choices. I do agree completely that by having cut grading based on beauty and light behavior is highly desirable. My own diamond cut class grading tool applied to the red area in the AGS cut grade graphic placed my highest grade "1A" completely inside the red portion of this graph, just like ACA diamonds do. My "1B" grade partially extended just a bit outside the red zone. My work was based on parameters and personal observation, not science.

I look forward to GIA, GCAL and IGI to get their acts together to make sensible decisions that mimic what is offered for round grading. A narrow Super Ideal, a bit broader "Ideal", a more commercial "Excellent" Cut and even a "VG" cut. Without any bias, I think many GIA XXX diamonds are very adequate for engagement rings and daily wear jewelry. Consumers should look closely at the choices and the costs. Admittedly, there are GIA XXX stones that miss the mark of being well cut. If you don't like the look, you should find another cut a little or a lot better.

Keep in mind, there is diamond rough with the potential for beauty far away from ideal parameters. Maybe those stones are not the greatest for symbolic items such as engagement rings, but they can be used with artistry in items that have superb visual interest and value. The market is being steered toward encouraging cookie cutter outlines, symmetry and appearances. It is in our human nature to categorize and grade things, but beauty and sentimental elements should continue to be personal to some extent and not formulated to reduce the diversity of choices for those who want choice versus conformity.

 

[Karl_K]

The AGSL system now used by GIA has a few serious short comings.
The biggest one is patterns.
This is less of an issue with a MRB but is absolutely critical with fancies.
With a MRB its the difference usually between a nice diamond and a super-ideal.
With fancies it can be the difference between blah and wow!
This is further complicated by the fact its not just face up patterns but how the patterns move and the stone dances with movement.
A fancy can have a great face up appearance but be a dud once it starts moving, another may be a bit of a dud face up but blow you away once it is moved.
It is much more complicated than a MRB.

Far more technical is the fact that the obstruction model in ASET is not very good, some say broken. This had to be done to simplify it into an easy to understand image.

Overall I find it to be a good system for the simpler and better understood MRB.
ASET images are useful for fancies but the grading part is not that robust.
A top of the line fancy may get AGS0 but its not the top of the line just because of the AGS0 grade.

 

[Texas Leaguer]

My feeling is that Super Ideal cuts have added value along with some added costs applied. AGS standard Ideal cuts have some added value an somewhat less added costs. Both kinds of Ideal cuts have the interest of a particular market at the retail level which hungers for "the best" and who can afford levels of luxury in their buying.

A far larger part of the diamonds market wants reasonably well cut, sparkly diamonds at a price that fits their ability and budget. This is the large market territory covered by GIA XXX to GIA VG.

Having sold many OEC and OM diamonds as well as all sorts of modern diamonds for 40+ years, I found personal pleasure in allowing retail stores and their customers to make diverse choices. There is no reason that round diamonds all must handle light and symmetry in a virtually identical manner. Consumers can handle making choices. I do agree completely that by having cut grading based on beauty and light behavior is highly desirable. My own diamond cut class grading tool applied to the red area in the AGS cut grade graphic placed my highest grade "1A" completely inside the red portion of this graph, just like ACA diamonds do. My "1B" grade partially extended just a bit outside the red zone. My work was based on parameters and personal observation, not science.

I look forward to GIA, GCAL and IGI to get their acts together to make sensible decisions that mimic what is offered for round grading. A narrow Super Ideal, a bit broader "Ideal", a more commercial "Excellent" Cut and even a "VG" cut. Without any bias, I think many GIA XXX diamonds are very adequate for engagement rings and daily wear jewelry. Consumers should look closely at the choices and the costs. Admittedly, there are GIA XXX stones that miss the mark of being well cut. If you don't like the look, you should find another cut a little or a lot better.

Keep in mind, there is diamond rough with the potential for beauty far away from ideal parameters. Maybe those stones are not the greatest for symbolic items such as engagement rings, but they can be used with artistry in items that have superb visual interest and value. The market is being steered toward encouraging cookie cutter outlines, symmetry and appearances. It is in our human nature to categorize and grade things, but beauty and sentimental elements should continue to be personal to some extent and not formulated to reduce the diversity of choices for those who want choice versus conformity.

Great post David. I agree with everything you said.

The only thing I would point out is that many consumers, especially those new to diamonds, get bedazzled in a jewelery store and may not have a full picture of what is available and what trade-offs they may be making as a result. For instance, many are told GIA EX cut grade is the best you can get. Even worse, fancy cuts with Ex Ex polish and symmetry are the best you can get!

GIA is in a position to be able to bring more awareness to the consumer market of the range of choice available to them.

 

[Texas Leaguer]

The AGSL system now used by GIA has a few serious short comings.
The biggest one is patterns.
This is less of an issue with a MRB but is absolutely critical with fancies.
With a MRB its the difference usually between a nice diamond and a super-ideal.
With fancies it can be the difference between blah and wow!
This is further complicated by the fact its not just face up patterns but how the patterns move and the stone dances with movement.
A fancy can have a great face up appearance but be a dud once it starts moving, another may be a bit of a dud face up but blow you away once it is moved.
It is much more complicated than a MRB.

Far more technical is the fact that the obstruction model in ASET is not very good, some say broken. This had to be done to simplify it into an easy to understand image.

Overall I find it to be a good system for the simpler and better understood MRB.
ASET images are useful for fancies but the grading part is not that robust.
A top of the line fancy may get AGS0 but its not the top of the line just because of the AGS0 grade.

Karl, you make an important point about patterns. There is a reason that AGS limited their focus to measuring brightness, contrast, fire and leakage. Scintillation has proven too complicated and/or too much in the realm of "taste". It was probably wise of them to exclude that.

I know AGS was involved in research on scintillation at the time of the acquisition so they may have progressed in their understanding enough to factor that in to whatever they eventually roll out.

But I also would not be surprised to see them leave that in the 'taste' category. That may be one of those things, to @oldminer 's point, that should continue to be left to the shopper's personal preference. Think of three well cut cushions for example - one is chunky, one is crushed ice, one is hearts and arrows. The extremely varied appearances are not soley a result of differences in brightness, fire, contrast and leakage! And each one could be ideal to three different shoppers.

 

[Ibrakeforpossums]

What a great thread!

 

[Rockdiamond]

Excellent discussion!
For regular readers, my views on this are out there.
A chart might look like this, if we're looking at Cushion Modified Brilliants


joking of course...but not all that much.
The range of table/depth combos that I've found appealing over the years....could be as shallow as 45%...or into the 70's
Table size can vary from 40's to 70's too.

An analogy....judging a true super ideal in a round is akin to a 100 yard dash, in the Olympics.
There's a clear goal... winner. There's no ( or miniscule) dispute about the desired results.
Trying to do the same for Cushions, radiant cuts, Pear Shapes., Emerald Cuts, ....is more like the artistic swimming events...where the judges decide based on certain parameters...but it's way more subjective.

Reading the excellent point made gave me a thought.
We all know what a "Super Ideal" is supposed to look like.
If there's some sort of visual attached to the grading system to show what the "ideal" goal is, it would serve a purpose for a large percentage of buyers.
Also - Oval probably represents the best candidate for standardization of all the fancy shapes. Also probably the second most popular shape lately behind rounds......so there's that. I get the motivation behind it.....just don't think it works for everyone.
I've always loved oddballs anyway, what do I know?

 

[Garry H (Cut Nut)]

Thoughtful article Bryan.
There are issues. I will post some from my PoV in separate posts incase there are discussion points of interest.
Firstly - it is impossible currently to search for GIA AGS on platforms.

 

[Garry H (Cut Nut)]

Another topic is transparency.
The GIA IBM clarity method is flawed. There is noting in the combination of these systems that will address that problem.
Severe graining like this GIA XXX D Flawless diamond with eye visible flaws for example:

 

[Garry H (Cut Nut)]

The AGS methodology is monocular. Humans have two eyes mounted horizontally. That dramatically changes the dark zones that AGS were way way too strict on.

And infact, as i demonstrated once to Jason Quick (the lead smart AGS scientist that the GIA poached and might solve the fancy shapes conundrum?) with an emerald cut diamond - their fancy shape EC did not work!

 

[Garry H (Cut Nut)]

Finally for now - As with the monoscopic example, the AGS method has a virtual 'head' obscuring 30 degrees and 40 degrees of the lighting hemisphere.
as shown below - 6 degrees (12 in the total hemisphere is enough) - is a long way from 40 / 2 = 20 degrees.
This is a fundamental flaw in AGS thinking. It was based on a crazy close up viewing distance used by the US military for close inspection (i.e. eye clean clarity).
As Karl knows from working on the new IGI Light Performance Grading Report with John Pollard, people look at diamonds from "half arms length" which means much shallower diamonds are generally preferred.