Side-by-Side Definition of Ideal Cut for a RB?

[GemView]

Good day!

I have been doing a lot reading lately on diamond cut grades. I ran across the specs for for what the GIA considers a Class 1 Make (not sure if I am repeating the terminology correctly, LOL). The AGS specs for grade 0 followed, and because of the side-by-side format on the Website that listed them, I noticed that the two labs had some differences in what would constitute an Ideal Cut. The site I was on—and I forget which one since I''ve been on so many lately—didn''t follow the GIA and AGS round brilliant ideal definitions with the other labs’ definitions of the same (IGI and EGL US, specifically).

Since the e-ring stone my boyfriend put a down payment on two weeks ago is graded by the EGL US as an "Ideal Plus", I compared the specs on the grading report for "our stone" to the definitions of Ideal posted here and elsewhere for the GIA and AGS. The stone we chose seems to share some aspects in common with the GIA Make/Class One and other aspects in common with the AGS 0.

With an HCA of 1.7, the quality of the cut is not so much in question, as I''m quite sure there are better to be found and a lot more being sold that would score far worse. My curiosity, however, is in the observation that the numbers on "our stone" seem to straddle the two sets of Ideal grading definitions attributed to the GIA and AGS. Could that observation explain why the EGL US report calls it an "Ideal Plus" instead of an "Ideal"? (BTW, is this terminology governed by FTC regulation or is it primarily an informal means for each lab to set their reports apart from one another?)

Without straying into a tangent about which labs offer superior grading, is there a straightforward breakdown posted or published for what the EGL US defines as an "Ideal" or "Ideal Plus" versus what the other U.S. labs (GIA, AGS, IGI) define as Ideal? Last but not least, I have what may be a hypothetical question for those of you who are appraisers/experts in the trade: Has anyone, to your knowledge, run a test—without the aid of a loupe or other device—to see if trained observers can visually differentiate the various lab “text-book Ideals” in a lineup of otherwise equal carat/color/clarity/polish/symmetry round brilliant stones? I guess what I''m getting at is whether or not the variances in brilliance/scintillation/fire (HCA numbers) would stand out to the unaided eye, such that someone could say, "There''s the GIA Class/Make 1" and "Here''s the AGS 0", and "Over there is the EGL US Ideal", etc.?

Thanks in advance for your input!!!! I''m a newbie, so please forgive me if I''ve asked a stupid or impossible question, LOL !

 

[oldminer]

My lab, AGA developed the most stringent and properly placed set of Ideal cut round diamond standards and has used them actively over the past 20 years. However, new technology, see www.imageminc.com, has now come into use in our lab and we have proof that even diamonds of identical cut parameters often do not perform identically. The small nuance parts we fail to measure may have a substantial effect on performance.

If an Ideal Cut really does not "Perform" to a very high level, then it is a failed stone. Just getting the parameters that one measures within Ideal bounds is what cutters have diligently been attempting to do while still saving as much weight as possible. This has lead them into finding every possible loophole in the theoretically perfect "Ideal Cut". There are tricks that have been discovered that produce parametrically correct stones which don't belong in the finest cut category.

We now test for PERFORMANCE and put parameters in a secondary position. You may find beautiful diamonds graded for fine cut with ANY lab's document, and you may find terrific inconsistency from that lab on other diamonds in terms of how well they perform with light. The whole game is changing and you are right where the action is.

With ImaGem, we can compare the apples, to the oranges, to the pears and to the peaches. It does not matter which lab graded the stone so long as the Performance can be measured directly. Picking a diamond you love should be the number 1 goal. It then can readily be checked out for its quality of Light Behavior.

My lab is not the only one doing this sort of light measurement. There are a growing number of places using different but somewhat related technologies. We have Consumer Gem Lab in FL using Gemex, GCAL using Diamond Profile and the recently opened GIL using another system I don't have the name of, both in NYC. One must be fair and mention these other groundbreaking efforts by independent appraisers.

I hope you will be helped by this. It is a confusing situation today. New standards are being created by new entities and not the GIA. We are all in a bit of a confused state right now.

 

[JohnQuixote]

The AGS has also concluded that, while proportions and measurements are helpful for making broad predictive judgments, direct assessment of a diamond''s actual light performance is more meaningful than numerical data and simulated predictions. They have now moved to performance-based grading rather than proportions-based grading and are using a reflector device called ASET (more info than you probably want, here.)

Much like Dave Atlas'' lab, AGS is committed to a judgement based on the actual diamond. This is because proportions sets do not account for patterning dynamics, girdle treatments, presence of facet yaw, etc.

This is not a new concept: For years many of us have been saying that an ideal-scope image always trumps an HCA estimation. This is the same premise.

Interestingly, after 10 years of experience with proportions-based cut grading AGS evolves to performance assessment - just as GIA is on the verge of introducing their first cut grading system based on (drum roll)... proportions.

 

[JohnQuixote]

GemView,

A more clear answer to your initial question is this:

AGS is the lab that set the standard called 'Ideal.' If a vendor is advertising a diamond graded by someone other than AGS as ideal it typically means that diamond meets traditional proportions sets AGS set forth for their 0 grade, and should have received top grade in polish and symmetry.

AGA had a system of grading cut as outlined by Dave Above. '1A' has been AGA's top grade.

GIA has never graded cut. They will start soon. 'Excellent' will be their top grade.

EGL, IGI, etc. have never graded cut.

Sometimes finish grades (polish and sym) have been misconstrued by people as representing an evaluation of cut.

 

[Dancing Fire]

Date: 8/1/2005 6:19:42 PM
Author:GemView

Without straying into a tangent about which labs offer superior grading, is there a straightforward breakdown posted or published for what the EGL US defines as an 'Ideal' or 'Ideal Plus' versus what the other U.S. labs (GIA, AGS, IGI) define as Ideal? Last but not least, I have what may be a hypothetical question for those of you who are appraisers/experts in the trade: Has anyone, to your knowledge, run a test—without the aid of a loupe or other device—to see if trained observers can visually differentiate the various lab “text-book Ideals” in a lineup of otherwise equal carat/color/clarity/polish/symmetry round brilliant stones? I guess what I'm getting at is whether or not the variances in brilliance/scintillation/fire (HCA numbers) would stand out to the unaided eye, such that someone could say, 'There's the GIA Class/Make 1' and 'Here's the AGS 0', and 'Over there is the EGL US Ideal', etc.?

GemView
EGL plays by a different set of "ideal rules" compare to AGS. can you post the specs?

 

[GemView]

Thanks for jumping in to address my question, oldminer. Having read the FAQ, the Imagem system sounds quite amazing. Is there any concern that having a totally automated process will put the human grading aspect out of the biz?

I would love to have our stone examined, but I''m not sure if the retailer will let us ship to your lab. Would that even be possible or would we have to have our retailer arrange it? (We''ve only put a down payment on it so far.) Alternately, do you know if this technology has been implemented anywhere on the West Coast?

I can only speak for myself, but I look forward to the day when the debate and subjectivity regarding the various certs has gone by the wayside. I haven''t seen anything here to that particular effect but there are Websites out there where the participants aren''t nearly so polite, professional and knowledgeable as the folks here at Pricescope. My regards!

 

[GemView]

"EGL plays by a different set of "ideal rules" compare to AGS. can you post the specs?"




Hi Dancing Fire,

Here are the specs for the stone, which we are going to have independently graded/appraised, shortly:


Depth 60.6%
Table 58%
Crown Angle: 32.9
Pavillio Angle: 40.3
Culet: None
F/SI1
Ideal Plus

It looks fantastic to our eyes and earns a 1.5/1.7 on the HCA depending on if you entere angle vs. percent.

Do you happen to know how the EGL US would define "Ideal Plus" vs. "Ideal"? Is it published or posted anywhere?

 

[GemView]

"For years many of us have been saying that an ideal-scope image always trumps an HCA estimation.  This is the same premise. Interestingly, after 10 years of experience with proportions-based cut grading AGS evolves to performance assessment - just as GIA is on the verge of introducing their first cut grading system based on (drum roll)...  proportions."

Thanks aslo for your input, JohnQuixote

I have some curiosity questions. Would you expect most retailers to have a Ideal-Scope or something that performs a similar function? (Apparently, our retailer does not. She is the owner, working in a jewelry conglomerate type B&M.) Also, has the GIA officially explained why they are just now moving toward cut grading? Do you foresee everyone in the diamond grading industry moving toward performance based standards in the next year—or do you anticipate that it may be slow to catch on?

 

[Slykat12]

I can say that as of one month ago no apprassor on the west coast that I could find had the fancy machines that Gog, roc doc and Dave Atlas has. I would heartily agree in sending your rock in for a light return test of sorts.

Dave when is the Ima gem gonna be ready for fancys?

 

[JohnQuixote]

Date: 8/3/2005 2:42:09 PM
Author: GemView
'For years many of us have been saying that an ideal-scope image always trumps an HCA estimation. This is the same premise. Interestingly, after 10 years of experience with proportions-based cut grading AGS evolves to performance assessment - just as GIA is on the verge of introducing their first cut grading system based on (drum roll)... proportions.'

Thanks aslo for your input, JohnQuixote

I have some curiosity questions. Would you expect most retailers to have a Ideal-Scope or something that performs a similar function? (Apparently, our retailer does not. She is the owner, working in a jewelry conglomerate type B&M.) Also, has the GIA officially explained why they are just now moving toward cut grading? Do you foresee everyone in the diamond grading industry moving toward performance based standards in the next year—or do you anticipate that it may be slow to catch on?

Gemview, you're welcome.

1. Retailers have been able to sell using eyes-only for many years. It is the advantage they will always have over internet/long-distance vendors. The internet caused proliferation of tools like ideal-scope (and now HCA has also been considered a strong aid for predicting a diamond's performance before seeing it. This is why INTERNET consumers know of these things, while many non-internet consumers do not.

Consider that most retailers with walk-in customers may not want reflector images 'confusing the issue,' since almost all of the buying public won't know to ask for them anyway.

With GIA adopting proportions-based grading you may see retailers begin to use information from the GCE (GIA Cut Estimator) to justify their in-house diamonds' cut grade - since a wide range will qualify for the top grade.

Retailers of ideal diamonds who use AGS for grading may or may use in-house ASET or other reflector devices/images (ideal-scope), depending on their customer base. If they have only walk-in customers they may not feel it's necessary. On the other hand, if they deal via internet - or are proud of their inventory - the additional info will help them to justify what they are selling.

Look to see many savvy B&Ms using GCE and a much smaller group with AGS0 quality goods potentially having ASET images.

2. GIA will stick with proportions. They will also allow many more diamonds to fall into their top grade. AGS will stick with performance and a stricter top grade. Do the math. Those with goods that receive top marks in both systems will promote both systems. Those with goods not performing well in AGS' metric will promote GIA's GCE and poo-poo the AGS' approach. Those with woofy, icky parameters will keep on keepin' on - and will poo-poo both systems.

 

[oldminer]

Kimberly: You asked: "Dave when is the ImaGem gonna be ready for fancys?"

Dr. Aggarwal, the chief inventor of ImaGem, is presently working at the ImaGem grading lab in Surat, India. He is utilizing the vast diamond inventories available to him there, as it is a major cutting center of diamonds. Many princess cut and marquise shaped diamonds come from that city and a full ImaGem lab has been set up in the diamond district there to create some income and to also utilize the diamonds that flow through the system for furthering the grading processes.

I expect, though I cannot promise, that princess cut and/or marquise cut will be added within a few weeks time to round diamond light behavior grading and cut grading via ImaGem both here and in Surat. I think you will see further ImaGem facilities around the USA and in Europe being opened in a few months, too. There is a lot of interest and a lot of talking going on at headquarters. They don''t tell me a whole lot, but there are many smiling faces among the principal partners and stockholders. I think there is a high degree of confidence in the direction that has been chosen.

 

[Garry H (Cut Nut)]

Hope it all works out well Dave.
You have had a long crusade for cut quality!


JohnQuixote, your advice and summation of the situation is excellent.

GemView I hope it makes sense (even though it doesnt)

 

[churchwedding]

Last but not least, I have what may be a hypothetical question for those of you who are appraisers/experts in the trade: Has anyone, to your knowledge, run a test—without the aid of a loupe or other device—to see if trained observers can visually differentiate the various lab “text-book Ideals” in a lineup of otherwise equal carat/color/clarity/polish/symmetry round brilliant stones? I guess what I''m getting at is whether or not the variances in brilliance/scintillation/fire (HCA numbers) would stand out to the unaided eye, such that someone could say, "There''s the GIA Class/Make 1" and "Here''s the AGS 0", and "Over there is the EGL US Ideal", etc.?

This is a very interesting question...I know PS has a study comparing the different lab''s grading of diamonds (AGS vs. EGL vs. GIa, etc.), but has there been any studies among consumers that shows that the un-trained eye can detect the differences between different types of ''ideal'' cuts...or even the difference between a few grades within the same system (i.e. AGS 0 vs. AGS 3)??

 

[Garry H (Cut Nut)]

The post pinned at the top discusses GIA survey.

AGS look at lots of diamonds too.

And I did my own for HCA

We all (now) get similar results - that there is a relationship between crown and pavilion angles, but where the limits are is quite different.

Unfortunately some of that thread has wandered off into very technichal science - but we keep bringing it back to the main topic.

All are welcome to join in.

 

[Dancing Fire]

Date: 8/3/2005 2:33:56 PM
Author: GemView
''EGL plays by a different set of ''ideal rules'' compare to AGS. can you post the specs?''




Hi Dancing Fire,

Here are the specs for the stone, which we are going to have independently graded/appraised, shortly:


Depth 60.6%
Table 58%
Crown Angle: 32.9
Pavillio Angle: 40.3
Culet: None
F/SI1
Ideal Plus

It looks fantastic to our eyes and earns a 1.5/1.7 on the HCA depending on if you entere angle vs. percent.

Do you happen to know how the EGL US would define ''Ideal Plus'' vs. ''Ideal''? Is it published or posted anywhere?

the specs (their ideal rule) should be printed on the EGL-USA report.