New Gia diamond cut grading system

[Fleimstaler]

Hi gentlemen.

I tried to find comments on the G & G article on diamond cut but I found none. Is there any comment on this topic somewhere on pricescope.com?
Thanks and Rgds.

Fleimstaler

 

[stretch4]

Gentlemen????

 

[orbaya]

Date: 1/6/2005 4:44:15 PM
Author: stretch4
Gentlemen????

LOL! I was thinking the same thing! I suppose I could start talking with a deep voice and glue a mustache to my face.

Oh, and I could use a marker to draw on a 5 o''clock shadow.

 

[JohnQuixote]

Date: 1/6/2005 3:43:32 PM
Author:Fleimstaler
Hi gentlemen.

I tried to find comments on the G & G article on diamond cut but I found none. Is there any comment on this topic somewhere on pricescope.com?
Thanks and Rgds.

Fleimstaler

Greetings Raffaele,

I have followed your discussions from this thread about Mr. Okuda with great interest. Welcome to PriceScope - it is nice to have you contribute.

GIA's new cut grading system will be announced sometime in 2005 (they have delayed it). Meanwhile, here is a link to the G&G Fall, 2004 article. Here is a link to GIAs online series of diamond cut articles, and here is a link to the diamond cut article archive.

I hope this is helpful.

 

[Garry H (Cut Nut)]

Leonid is in the process of putting a 20 page review onto the http://journal.pricescope.com/ journal article. Give him a few days - it is a lot of work and he is rather busy.

There are several other topics that i have generated discussing GIA and AGS cut grade systems over the past 6 months.

this chart is from my article - it shows that there will be some surprises.Basically they will use a 5 grade system - but the 5th and worst grade is very very soft - so it may really only be a 4 grade system - a bit like symmetry - when was the last time you saw a stone with a Poor sym grade?

BTW this chart is not gIA's - it is my interpretation and already you can see they have given some e.g's that fall outside the ovals I have drawn over the HCA chart

 

[Rhino]

Here''s a link to a summary on the study done on fire by JCK.

http://www.professionaljeweler.com/archives/articles/2002/jan02/0102dg.html

 

[lostdog]

I'll need to read it a few more times, but I am trying to get my head around these findings from the study linked above (note DCLR= "dispersed colored light return", a way to address "fire" as “the visible extent of light dispersed into spectral colors.” see the link for much more) :

"DCLR is highest for a 34 crown angle combined with a star facet length of 64%-65%.
DCLR showed dramatic increases as lower girdle facets increased in length 45%-85%. "

As usual, this takes some pondering (on my part, at least). What do these percentages imply about the geometry of the cut in general?

- -

Also, interesting, but more predictable:

"DCLR in general increases as crown angle increases.

DCLR in general decreases as the pavilion angle increases.

DCLR in general decreases as table percentages increase."

- - -

A concern with the study is that is sounds like much analysis was done by computer with limited human perception figured in. But it does seem to be another significant step on the journey toward mapping the cut/performance territory in greater detail, eventually to unify the various visual aspects similar to what HCA does now broadly.

 

[Fleimstaler]

Hi Gentlemen.

Thanks John for your wlecome and the greetings. I think that greeetings cheer up, right?

By reading the article on the Fall 2004 issue of G & G, I had the following impresisons:

The new GIA diamond cut grading system is based upon:

1. Proprtions
2. Okuda'' red light reflection principle
3. Gemprint techonology

This came immediatly to my mind because this is the system that I have been used for meny years.

I may be wrong but we will see when GIA pubblish thier final results.

If this is the system it must be revised whithin a short time because is not complete.

Rgds.

Fleimstaler

 

[denverappraiser]

Date: 1/7/2005 7:49:30 AM
Author: Fleimstaler

By reading the article on the Fall 2004 issue of G & G, I had the following impresisons:

The new GIA diamond cut grading system is based upon:

1. Proprtions
2. Okuda'' red light reflection principle
3. Gemprint techonology

Rgds.

Fleimstaler

Fleimstaler,

Can you explain what you mean please? The red reflection is an interesting way to observe some of the attributes of a stone but I didn''t see it discussed in the G&G article about establishing a grading system and certainly not as a basis for the new grading. Similarly, can you please tell us more about the connection you see with Gemprint.

Neil Beaty
Independent Appraisals in Denver

 

[oldminer]

Just to put a little different spin and perspective into this topic, I am going to spend a moment with the upcoming ImaGem Light Behavior and New AGA Cut Class grading structure that will debut on 1/20/05. AGA will interpret the ImaGem actual light measurements into 6 Light Behavior levels. O will be the best grade down to a GIA-like broad grade 5 which will encompass approximately the bottom half of possible Light Behavior qualities. Truthfully, only diamonds scoring well into the upper ranges of the upper half will be of much interest to the trade or consumers, so why waste effort on informing people how badly a stone performs when that question won''t be asked. People will want to know how well diamonds represented as finely cut do perform and we will have directly measured results to provide.

In combination with being able to actually measure Brilliancy, Sparkle and Intensity via ImaGem, AGA will use parametric limiting conditions which limit the durability, beauty, or width to depth (apparent size to weight) relationship. These limiting conditions will be very much more liberal than the original AGA system, which was accurate, painfully so, but highly conservative, because we could not measure light performance. Now, with Light Behavior physically measured, we can simplify and liberalize the range of possible cut shapes.....If a diamond is durable, has a good weight to diameter relationship, and has a proper finish, we can now grade it fully. A top grade ImaGem/AGA stone will be a 01A....

With ImaGem what we don''t need to do is measure every facet to death. We don''t have to look at every possible parameter to predict what the Light Behavior is. With ImaGem, we simply MEASURE Light Behavior. We don''t calculate a theoretical light reading based on parameters. The best example I can give you to prove what ImaGem is doing makes sense, is the fact that we weigh diamonds. We do have pretty good formulas for estimating their weight, but we have invented scales that not only are much more accurate, they are faster than calculating an approximate weight. The ImaGem unit is the scale upon which one measures light performance and there is no need to spend futile time in calculating what "might" be taking place. What if you don''t measure something of importance? What if you mis-measure something? What if the stone is a tiny bit cloudy? What if an inclusion has an effect on Light Behavior? These questions are important enough to make one realize that calculating light behavior will be of more interest to designers of cutting styles, but of far less gemological interest in grading diamonds. AND, Grading Diamonds is What We Do.

 

[Fleimstaler]

Hi Neal.

To answer your question is necessary to ask you one.

Please look at the first stone N. RD01 of the first category of the example shown in the article of the Fall issue 2004 of G & G, the stone has the following proportions:

table size 54%
crown angle 34.0°
pavilion angle 40.8°
crown height 15.5%
star length 50%
lower girdle length 75%
totale depth 61.2%


and please also look at the first stone of the second category N. RD 16

table size 53%
crown angle 33.5°
pavilion angle 40.6°
crown height 15.5%
star length 50%
lower girdle length 75%
total depth 61.2%


They are exactly the same. I think that is very difficult to find two stone with the same proportions.

What is the difference between the two stones? Why are they in two different categories?

If graded according to the proportions they would have scored the same grade right?

What is the difference then? And how can it be assesed?

Why did GIA pubblish such an example? To my opinion just to show readers that two stones with the same proportions do performe differently that they the technology to differentiate.

To my opinion it can be assesed by the Okuda red light reflections principle from which , the firescope, ideal scope, my instruments and so on derive. This is my opinion because I have used for many years.

Applying this principle you differentiate between the two and you and realise how great the difference between the two is.

The Gemprint techonlogy contains in itself all informations but it is difficult to extrapolate them, but it may be done.

On diamondtalk. com a few years ago, if I remmeber correctly, a gentleman named (I think) David Atlas (I may remember wrongly) offered for sale his gemprint for 100 USD and I offered to buy it, but, as he never answered to my offer, I bought the gemprint from Wink Jones.

I am ready to buy another one if anyone is ready to sell it for a reasonable price.

I am sorry not to be willing to be more specific on this issue, but allow me for the moment to hang on it.

So, my guess of the GIA cut system, is what I have outlined above, as I know it well as I have used it for many years and then I revised as outlined below.

The revision of this system, if they want it to be complete, (and if the system is as I guess) they have to
a. severe the link with the proportion concept as applied now
b. apply to fancy cuts as well

Thanks and regards.

Fleimstaler

 

[oldminer]

Raffaele:

I am the David Atlas you mentioned above. Can't think of why I would not have sold you the old Gemprint I once had in the office. In the end, I threw it into the trash as I never thought I ever found anyone who wanted it....I'd certainly have taken your $100 if I had known about it...Oh well. I don't miss the old Gemprint device. While I think it worked, the Gemprint firm has never successfully marketed their product.

GIA and others will not "sever" the ties to proprtion grading since there are some proportions that are "faulty" Even if there is superb light return, a diamond with certain proportion faults should NOT score as a top quality in "CUT". A diamond that is overly deep, one that is dangerously shallow in the crown, one with a heavy girdle, one with more than a medium culet....those kind of faults prevent a diamond from being the "best".

Fancy cuts need to meet similar, but thoughtfully modified, parameters, too. The light return from some super fine fancies might be as high or higher than from super fine rounds. We don't even know what to expect right now. We'd willingly predict that most fancies will underperform fine rounds, but some few may be equal or even better.

The grading of cut is not solely "light performance", but is also comprised of data indicating a diamond has been properly crafted to look its best and to last a long time. All the major labs agree on this. How it all will come together is just being discovered.

 

[denverappraiser]

Raffaele,

I guess I''m missing your point. They are the same except for table, crown angle and pavilion angle. GIA''s point in their example was to indicate that these are important attributes. Yours seems to be that they''re not.

I would love to hear more about how to extrapolate useful cut information from the Gemprint scans. I agree that useful data probably there but I''ve seen nothing from Gemprint or anyone else about interpreting the scans for cut grading purposes. They market the system as a way of identifying individual stones. This is useful but it''s an entirely different application. Adding cut grading functionality would be very helpful.

If anyone whats to sell their gemprint system for $100, call me. I''m interested. I can''t say much for the old polaroid based system but the the system that has been in use for the last decade or so is worth far more than that and I would be happy to have more than one.

Neil Beaty
Independent Appraisals in Denver

 

[oldminer]

From a single laser beam perpendicular to the table at the approximate center point of the stone, I doubt you could extrapolate much about cut quality that would be accurate and/or worth the effort. You could more with a flashlight and the naked eye, but maybe I am being a little cynical.

My old Gemprint was the original 1981 version, a long unit with Polaroid film. It was impressive although my father remained unimpressed by all except how costly it had been. The newer ones are better, no doubt. They just never gained a big market recognition factor and that would have made a big difference to all of us that had these devices. All diamonds processed through ImaGem facilites will be able to be immediately "registered" in a central database as to their identity and ownership. This will duplicate the concept of Gemprint''s registration, but not require any additional hardware. I would expect the same companies that offer a Gemprint discount to begin offering the ImaGem discount at some point down the road. These insurance company negotiations may well be part of ImaGem''s marketing plan.

 

[denverappraiser]

David,

I would expect the Gemprint to be very interested in any research that Raffaele has done in using their equipment for cut analysis. I certainly agree that there are some severe limitations and perhaps this is why their own research hasn't led to any changes in how they market their system. Hopefully this is the break that they've been waiting for.

The threat of new competition for their registration system from Imagem is, I'm sure, an area of concern for the good folks at Gemprint. No doubt they are anxious to see the details when they become available. 1/20/05 you say? Will it be possible to see the Imagem system at Tucson?

Neil Beaty
Independent Appraisals in Denver

 

[oldminer]

ImaGem will not be on display in Tucson. I would expect future major shows will see ImaGem on display, but I don't know when they will begin this aspect of their plan.

There is a major diamond cut educational event hosted by the Accredited Gemologists Association on 1/2/05 at the Tucson University Park Marriott and I will be there hopefully accompanied by Dr. Lalit Aggarwal, the inventor and principal of ImaGem. He or I may be part of the panel assembled for the day. Again, this is all lat minute manouvering and I'm not certain of the exact committment that is being formulated. POLITICS>>> This Accredited Gemologists event is bound to be one of their best ever. It is an excellent continuing eduction orgainzation than has never gotten the recognition it so well deserves. Attendance is open to all and the fee is nominal. considering the location, length of the day long event and the topic. Generally speaking, the members are among the friendliest folks in the gemology biz. Of course, there are exceptions to this rule........they know who they are.

 

[Regular Guy]

Not wanting to steer this topic away from it''s course...but seems like it may already be there...

Dave, curious about your new system...

Is it a cross between the Imagescope and the Brilliacescope?

With:

a) both yielding output to understand light performance
b) and with the Imagescope clearly just passively displaying/explicating light performance, but with no quantitative aspect, and
c) with the Brilliancescope being quantitative, and based on aspects of the physical diamond, but still projective and assumptive of how the light performance should be, based on a read of some of its specific characteristics

with your tool bringing together some of these quantitative and non-projective aspects of light measurement?

PS Congrats on the "king of the hill" reading of web use...clearly based on your good work and hard work...with best wishes.

 

[belle]

Date: 1/7/2005 1:42:17 PM
Author: oldminer
ImaGem will not be on display in Tucson. I would expect future major shows will see ImaGem on display, but I don''t know when they will begin this aspect of their plan.

There is a major diamond cut educational event hosted by the Accredited Gemologists Association on 1/2/05 at the Tucson University Park Marriott and I will be there hopefully accompanied by Dr. Lalit Aggarwal, the inventor and principal of ImaGem. He or I may be part of the panel assembled for the day. Again, this is all lat minute manouvering and I''m not certain of the exact committment that is being formulated. POLITICS>>> This Accredited Gemologists event is bound to be one of their best ever. It is an excellent continuing eduction orgainzation than has never gotten the recognition it so well deserves. Attendance is open to all and the fee is nominal. considering the location, length of the day long event and the topic. Generally speaking, the members are among the friendliest folks in the gemology biz. Of course, there are exceptions to this rule........they know who they are.

am i stuck in the twilight zone? (the answer my still be yes) what is the date of this educational event in tucson? and where can i get more information about it? thanks!

 

[denverappraiser]

www.accreditedgemologists.org

I''ve been a member for years. Hopefully I''m not the exception that Dave mentioned.


Neil Beaty
Independent Appraisals in Denver

 

[oldminer]

Yes, I sort of stole the thread. I apologize (a little bit).....Please forgive me.

The ImaGem does not use the additive strategy of the Brilliancescope and it does give quantitative numbers on Light Return, Sparkle (Scintillation), and Intensity (Pattern). These quantitative numbers are highly repeatable and characterize the stone. As with most things humans observe, some degree of balance and moderation create the most beautiful and attractive thing. A diamond that is all light return would be like a light bulb or a flat mirror, but not beautiful. One with too much or too little scintillation won''t be the best. One with a lot of intensity will be better than one without enough and too much intensity, while it is difficult to put into a short explanation, is not going to be a superb stone, either. To go from numbers into "grades" is a gemologist''s challenge and it has been a long term effort to remove most of the subjectivity.

When one talks about beauty, or most beautiful, it remains an inherently subjective thing. There is no one set of parameters or measures that everyone would agree provides the ultimate beauty content. It is a series of results that give pretty much (subjectively) the best range of highly beautiful diamonds which converts to diamond grades for Light Behavior.

No one will prevent someone who can''t see or appreciate the difference from liking and buying a grade 2 stone because it looks nice to their eyes and fits their personal budget. We do need to categorize the results in a consistent fashion, and I think we will be able to do that very cleanly.

ImaGem does not have a predictive element. It is pure data and numerical information, but it is based on science from folks who understand human perception and statistical analsysis. With statistics combined with technology comes accuracy and dependable results.

 

[Garry H (Cut Nut)]

Date: 1/7/2005 4

8:32 PM
Author: oldminer
Yes, I sort of stole the thread. I apologize (a little bit).....Please forgive me.



When one talks about beauty, or most beautiful, it remains an inherently subjective thing. There is no one set of parameters or measures that everyone would agree provides the ultimate beauty content. It is a series of results that give pretty much (subjectively) the best range of highly beautiful diamonds which converts to diamond grades for Light Behavior.

Why is it my sick mind turns your thoughts into appraisal of the opposite sex thoughts Dave.

Can anyone recomend a therapy that would cure me?

 

[Garry H (Cut Nut)]

Rapaport has an article too - there are photo''s in the hard copy - but none on the website.
Here is an excerpt:

http://www.diamonds.net/news/newsitem.asp?num=10932&type=all&topic=GIA&searchfor=cut&author=

Results from Computer Modeling and Observation Tests
The GIA researchers based their findings on the results of the two main parts of the research project: computer modeling to predict which sets of proportions would yield the best results under specific lighting conditions; and extensive visual preference tests conducted with a wide variety of trade and non-trade observers to determine the ability to consistently discern face-up appearance aspects (brightness, fire, and scintillation) and the importance of other cut-quality components (such as durability and finish).

The results of the preliminary computer modeling for brilliance and fire were reported in Gems & Gemology (articles cited earlier and available at http://www.gia.edu/ gemsandgemology/27540/free_article_downloads.cfm). Comparison of those results to observations of actual diamonds in similar conditions allowed the researchers to refine these metrics. Further observation tests evaluating overall appearance — made by representatives from all levels of the diamond trade in controlled viewing environments — also confirmed that those two aspects alone were insufficient to predict the appearance of many diamonds.

“Our initial observation tests revealed that, as we expected, our best brightness and fire metrics were able to predict specific observation results (i.e., brightness and fire), but they were not adequate to predict and evaluate a diamond’s overall cut appearance and quality,” wrote Moses and his colleagues.

 

[valeria101]

Date: 1/7/2005 6:46:49 PM
Author: Garry H (Cut Nut)

Rapaport has an article too - there are photo''s in the hard copy - but none on the website.
Here is an excerpt:
[...]
“Our initial observation tests revealed that, as we expected, our best brightness and fire metrics were able to predict specific observation results (i.e., brightness and fire), but they were not adequate to predict and evaluate a diamond’s overall cut appearance and quality,” wrote Moses and his colleagues.

Well, spot on... philosophy by the book. Who could disagree ?

When they say "overall cut appearance", that cannot be a photographic representation like the GA does, right ? ''Cause those are naked, perfectly predictable numbers really.

 

[Garry H (Cut Nut)]

Ther photo''s are pretty basic.
This is the second catagory candidates from my article that will appear in the journal section when Leonid has time. GIA''s photo''s are near the bottom

 

[Superidealist]

Date: 1/7/2005
Author: Fleimstaler

To my opinion it can be assesed by the Okuda red light reflections principle from which , the firescope, ideal scope, my instruments and so on derive.

Again, it seems that this technique of evaluating cut predates even Okuda''s microscope. To credit him with originating it ignores this.

 

[lostdog]

Both from http://www.gia.edu/gemsandgemology/18578/21572/2232/back_issue_article_detail.cfm :

"Although there actually has been a tremendous amount of industry interest in the creation of an objective, scientifically based system for assessing diamond cut, ultimately the decisions on this project and the directions GIA has chosen were derived from its mission—to ensure the public trust in gems and jewelry by upholding the highest standards of integrity, academics, science, and professionalism through education, research, laboratory services, and instrument development. GIA firmly believes that the public interest is best served by creating such a system, and that its impact on the trade will also be positive."

But think about:

"Diamond manufacturers will be able to cut round brilliants to a wider range than the current norm and still achieve top-grade, great-looking diamonds. An even wider range of proportions can produce pleasing diamonds in the upper-middle to middle grade ranges. Each of these grades will, in many cases, allow for greater yield and weight retention from the rough."

 

[valeria101]

Date: 1/8/2005 3:198 AM
Author: lostdog

But think about:

''Diamond manufacturers will be able to cut round brilliants to a wider range than the current norm and still achieve top-grade, great-looking diamonds.

Well... if only AGS0 proportions would look good, almost no one would like diamonds, no ? Narrow grades serve branding well, but there must be some good in a broader spectrum. At least IMO.

As long as rough is bought by weight not "potential output of ideal cuts" there is logic to sell the cut material by weight too and keep it havy. Shapes are priced by yeild anyway, it''s not that lighter ideals are any cheaper ''cause they weight less. They are nicer, relatively large, but lighter. The other stuff still sells, it seems

- for now.

 

[Fleimstaler]

Hi Neil!

Let us compare the:




table size crown angle pavilion angle crown height
stone RD01 54% 34.0° 40.8° 15.5%
stone RD16 53% 33.5° 40.6° 15.5%

difference 1% 0.5° 0.2° none

Now, these differences applied to a very small quantity (diameter of the stone) count for a nearly impossible quantity to be measured.

The above shown differences could be found on the same stone if the measurments were taken by two different persons and even, by two different instruments.

How can it be that if absolute accuray is expected that twoo stones have different table (1%) and crown angle (0.5%) but have the same crown height? 15.5%

How can it be that the two stones have differnt pavillion angle (0.2°) but the same total depth? 61.2%

Very simply: because these differences count nothing.

There no perfect measurments but all are precise within a certain probable error that could be assesed also on measuring a stone. As there have never been any need for such accuracy in measuring the proportions of a stone it has never been done because the two stones by any lab, be it GIA, AGS or HRD, would have been graded exactly the same.

I think, and this is my personal guess, that GIA showed the two stones in rwo categories just to show that there might be two stones with the same proportions but have a different light performance and that they can differentiate bettween the two and in this way justify the progress of a new graing system.

Regarding your wish to have some informations about the Gemprint, I will try to post some photos, but allow me some time as I cannot do it myself and have to ask someone to do it for me and, furthermore I have to look into my archives and find the right ones.

Thanks and best regards.

Fleimstaler

 

[Garry H (Cut Nut)]

Sorry F you missed the devil hiding in the detail.
This stone was downgraded because of ‘Good’ polish - the top grade must have Excellent or Very good symmetry under the proosed "Foundation" rules.
In addition GIA claimed combined proportions made the pavilion mains look very dark. In my opinion, with this small table, lengthening the LG’s (to 85%) would improve this diamonds appearance. The table looks very dark because of the combined effect of the short Lower Girldes and the smaller table.

 

[lostdog]

"Narrow grades serve branding well, but there must be some good in a broader spectrum. At least IMO."

Broader spectrum for each grade, I agree with, too. It's performance-based (in some manner), so should grading should follow performance.


"Shapes are priced by yield anyway, it's not that lighter ideals are any cheaper 'cause they weight less. They are nicer, relatively large, but lighter. "

You know a lot more about this than me, but doesn't this open the door to greater carat weight for same visual size and performance? And from the economics aspect, does it raise the price for the same visual result (if cutters aim to max carat weight while still delivering ideal grade?) ? Or tend to decrease spreads overall ? (given the consumer's fixation on certain benchmark carat numbers.)

I guess your point is that it's related to the same theoretical rough delivering the equivalently graded cut stone at either weight. Cost to create it is about the same. Yield just went up. But will cost of ideals then drop per carat? That does't sound right. (Maybe I'm not sure what position you are taking.)

"Each of these grades will, in many cases, allow for greater yield and weight retention from the rough"

So it's not just the ideals, either. The whole new system delivers (or can deliver) more graded cut weight from given rough. If pricing on yield is based on certain assumptions about what sort of grade/weight is the result, and now that ratio changes, a higher grade and weight is possible from the same rough, and the price to yield equation changes.

What's the impact on the market, do you think?

It's hard not to be cynical and conclude that consumer's options for buying the better grade stones just got visually smaller or more expensive or both.