AGS Releases New Cut Grades for Rounds

[Rhino]

Just got the CD yesterday. A cursory review shows that they will also take minor facets into account. Many proportion combinations currently considered ideal will not be. The tables are broken down by their table sizes starting from 47% up to 70%. The results given on each of these charts are for rounds with lower girde length at 80%, stars at 50% and girdle thickness at 3.5% at the mains. For those with DiamCalc, a diamond with an 80% lower girdle length is similar to 83% lower girdle depth. For a discussion of the differences between lower girdle depth vs lower girdle length pm me and I''ll forward you details.

One observation I''ve taken note of (which is not surprising) is that as the tables get larger, there is less selection of combinations for an ideal.

Is it certainly more anal however it appears this is going to be way more accurate than the model they currently have in place. I''ll share more as I test more and compare their results with other known optical performers. So far I like what I see.

 

[valeria101]

So... GIA will report minor facets, AGS will as well...

Based on the current releases about their up-comming standards, is there any way to know if the two venerable institutions agree ?

And, in the meantime, how can equivalent info be obtained about the current stock ? Is it possible at all ?

 

[Colored Gemstone Nut]

Maybe I am out of the loop Ana

, but I have not heard of Gia making any changes to their reports to include minor facets and for anyone "in the know", are they going to be posting more in depth measurements already available like on AGS certs..

 

[valeria101]

Date: 2/2/2005 4:30:16 PM
Author: Colored Gemstone Nut
Maybe I am out of the loop Ana ,

I don't know what the new reports might look like and when they would come out. Their cut study does take minor facets into account though.

 

[Paul-Antwerp]

Jonathan, beware,

The AGS-CD, which you and I and many others received, are "cutting guidelines". This should not be confused with "grading guidelines".

This CD is meant to give cutters an indication in which area they should cut in order to obtain a specific cut-grade. These guidelines are necessary in order to plan the rough.

When grading, AGS will not take these charts into account. They will measure the stone (Sarin, possibly Helium), and introduce the 3D-measurement into specific AGS-software. At that point in time, we are not looking at average angles anymore, but at the real 3D-stone. This could mean that one could have stones with all average measurements in the 0-area of the cutting guidelines, but that the actual stone does not get the 0-grade. Or the other way around.

As you can see, the charts work with steps of 0.2°, but this will not be the case in grading either. In the princess-charts, the top-grade-area combines the 0 and 1-grade, which is another complication.

This of course also creates problems when looking at currently available stones and at stones with a report from another lab and a Sarin-measurement. Even when using these "cutting guidelines", one has to be cautious, because these are indeed not "grading guidelines".

I understand that, at some point in time, AGS will also release the software to cutters, so that they can measure a stone, and introduce the 3D-scan into the software, in order to assess the cut-grade before shipping it to AGS. At that point in time, a dealer possessing a good Sarin and the AGS-software and the stone of course, can assess the AGS-grade of a non-AGS-graded stone.

GIA will probably work in a different way. They have carried out their cut-studies, and have worked everything back into parameters, including those of the minor facets. Most probably, they will measure a stone, take the average proportions, and check those in their parametrical charts, to get a grade. With only 5 possible GIA-grades, compared with the 11 of AGS, and with much more industry pressure on GIA than on AGS, one could foresee that both institutions will basically be on a similar line on the way of cut-grading, but the top-grade of GIA will certainly be a lot broader than that of AGS. Carefully looking at AGS'' charts, I have to say once more that it will take master-planners and a very dedicated organisation to obtain AGS-0 consistently.

Live long,

 

[Bagpuss]

Quote "With only 5 possible GIA-grades, compared with the 11 of AGS, and with much more industry pressure on GIA than on AGS, one could foresee that both institutions will basically be on a similar line on the way of cut-grading, but the top-grade of GIA will certainly be a lot broader than that of AGS. Carefully looking at AGS' charts, I have to say once more that it will take master-planners and a very dedicated organisation to obtain AGS-0 consistently" Paul

Does this mean that it's likely that AGS-0's will be more sought after than GIA top-grades because of the tighter tolerances? If so, would this also mean that AGS might come to be seen as the stricter therefore 'better' lab?

 

[diagem]

Please excuse my knowledge in cutting,

I never heard the term MINOR FACETS, can someone please explain?

Thanx in addvance.

 

[pqcollectibles]

Thanks much, Paul, for the clarification. Rhino''s initial post made me more than a bit nervous. I was pulling out the Sarin and checking my stats to see if my diamond would no longer be considered an AGS Ideal.

Date: 2/3/2005 9:30:50 AM
Author: Bagpuss
Quote ''With only 5 possible GIA-grades, compared with the 11 of AGS, and with much more industry pressure on GIA than on AGS, one could foresee that both institutions will basically be on a similar line on the way of cut-grading, but the top-grade of GIA will certainly be a lot broader than that of AGS. Carefully looking at AGS'' charts, I have to say once more that it will take master-planners and a very dedicated organisation to obtain AGS-0 consistently'' Paul

Does this mean that it''s likely that AGS-0''s will be more sought after than GIA top-grades because of the tighter tolerances? If so, would this also mean that AGS might come to be seen as the stricter therefore ''better'' lab?

I wonder the same thing too, Bagpuss. So many jewelers and diamond Vendors have the "GIA Cert is the best" mentality. Will this move make AGS more widely accepted by both Vendors and consumers than is the case currently??

 

[Paul-Antwerp]

Bagpuss,

One could foresee that the GIA-top-grade will contain a number of AGS-grades. One would expect that AGS-0, 1 and 2 would definitely be in the GIA-top-grade.

However, looking at the AGS-charts and the current info on the GIA-system, I have the impression that even some AGS-4 and AGS-5-stones will get the GIA-top-grade.

There is no doubt that, as far as cut is concerned, AGS will be regarded as the stricter and better lab.

Live long,

 

[Bagpuss]

Thanks for clarifying that Paul.

pqc - I'm sure there are a lot of nervous GIA ideal cut owners out there, but really, if their diamonds were lovely when they bought them, they're still going to be lovely now. Though on the other hand I can see that those who want or need to be able to say - I have the best of the best - or those who feel they may lose money with the introduction of different cut grades, will be watching these developments keenly.

Although the whole cut thing interests me, I refuse to let myself get too hung up on numbers/grades of any kind. Beautiful diamonds are my only goal.

 

[JohnQuixote]

Date: 2/3/2005 9:36:36 AM
Author: DiaGem
Please excuse my knowledge in cutting,

I never heard the term MINOR FACETS, can someone please explain?

Thanx in addvance.

In the past proportions grading has used average angles of crown and pavilion construction.

Minor facet analysis typically concerns construction particulars of the lower girdle (pavilion) and star (crown) facet lengths.

Here is a page showing where those facets lie on a diamond.

 

[diagem]

I understand that minor facets are part of the brillianteering facets, just categorized with different names.

Thanx,

 

[pqcollectibles]

Date: 2/3/2005 10

6:31 AM
Author: Bagpuss
Thanks for clarifying that Paul.

pqc - I''m sure there are a lot of nervous GIA ideal cut owners out there, but really, if their diamonds were lovely when they bought them, they''re still going to be lovely now. Though on the other hand I can see that those who want or need to be able to say - I have the best of the best - or those who feel they may loose money with the introduction of different cut grades, will be watching these developments keenly.

Although the whole cut thing interests me, I refuse to let myself get too hung up on numbers/grades of any kind. Beautiful diamonds are my only goal.

I agree with your sentiment, BP. I currently have AGS graded Ideals. I won''t love them any less if the new system revises that status, but I''ll be mentally more comfortable if the grading of my diamonds stays the same. Most especially my ring diamond.

 

[Rhino]

Thanks for that Paul. I thought releasing info with *only* 80% lower girdles and 50% stars was a little too limited. Let me ask though ... on these charts ... if it states that a 56 table, 35 crown, 41 pavilion is a 2 (out of 10 or 11) are you saying that that is NOT what it''s going to be? They have grading numbers all over the chart for many various proportion combos.

Please clarify.

Peace,

 

[Paul-Antwerp]

Date: 2/3/2005 10:53:33 AM
Author: Rhino
Thanks for that Paul. I thought releasing info with *only* 80% lower girdles and 50% stars was a little too limited. Let me ask though ... on these charts ... if it states that a 56 table, 35 crown, 41 pavilion is a 2 (out of 10 or 11) are you saying that that is NOT what it''s going to be? They have grading numbers all over the chart for many various proportion combos.

Please clarify.

Peace,

Hi Rhino,

As you notice, the title of the chart also says ''for a 6 millimeter round brilliant''. I am not sure, but it might indicate that the chart is not only different for other lower girdles, and/or stars, but also for other sizes.

So, with a different lower girdle length and/or star size, maybe for another size, this combo might be a 0 in stead of a 2.

And for sure, if everything is like the chart, including lower girdles, stars and size, one still has the possibility that there is to much variation between individual facets (while the averages give it a 2), that the 3D-scan would give it another grade.

Therefore, the indicated grade of 2 is a strong indication of the final grade, but there is sufficient room for the final grade to be better or worse. For that, we have to get the final software, and be able to take a 3D-measurement, in order to introduce it into the software.

Live long,

 

[Rhino]

Very interesting Paul. Thanks for that. I have heard that GIA will be releasing the software for free within the trade wherein the models could be imported into their software. Perhaps AGS will do something along the same lines. I would imagine since Sarin is so commonly accepted, that their models will import into both pieces of software. I also like the fact that AGS will not only be taking into account minor facets but also variances as well. THIS EXCITES ME.

In any case ... for those of you PS''r''s who have been purchasing your diamonds based on optical properties ... I don''t think ya''ll have anything to worry about. Those vendors who hand select their stones based on optical characteristics (and not necessarily numbers alone) have steered you in the right direction so there should not be any surprises.

PQ!!! It''s good to see you around. I''ve been a lil busy here and not posting as much as I''d like but it brought a smile to my face to see your friendly name here on the boards.

Peace,

 

[Rhino]

Just to add a tad to Sir John''s answer. The minor facets on a standard round brilliant ...

16 upper girdles (pictured in yellow)
8 stars (pictured in blue)
16 lower girdles (pictured in red).

They constitute 40 out of 57 facets (or 58 if there''s a culet). Hope this helps.

 

[valeria101]

Date: 2/3/2005 3:40:43 PM
Author: Rhino

In any case ... for those of you PS'r's who have been purchasing your diamonds based on optical properties ... I don't think ya'll have anything to worry about.

Any reason why the cutting and the cut grading guidelines by the same lab would not be in perfect accord (including date of release & all) ?

 

[Paul-Antwerp]

Date: 2/3/2005 8:58:42 PM
Author: valeria101

Any reason why the cutting and the cut grading guidelines by the same lab would not be in perfect accord (including date of release & all) ?

That is simply because cutting is not an exact science. If we are cutting for a main pavilion angle of 40.7°, it is very rare that we achieve 40.7 on all 8 facets. And you must remember that we are heading the pack in our search for precision.

Now, the grading of AGS will be done on the full 3D-stone and its light performance. But is impossible to instruct a cutter to cut for light performance. It is like instructing a constructor to build a beautiful building. A cutter needs angles in order to perform his job. And these cutting guidelines is very important helpful information for a cutter, so that he can better plan the rough stone, and aim for a specific grade.

But because there always is a difference between the goal and the real outcome of the cutting process, one cannot take the cutting guidelines as a guarantee for the grading outcome. It depends on how far the actual cutting deviates from the guideline. Even with the averages inside the cutting guidelines, one can have serious deviations between individual facets, and the grading in 3D will pick this up, and give a different grade.

The cutting guidelines are therefore what they are, cutting guidelines. AGS'' grading will be software-driven, and on the 3D-measurement of the stone, and it is incorrect to use the cutting guidelines to put a grade on a non-AGS-stone.

I think that it is very important for consumers to understand this.

Live long,

 

[Lynn B]

The more I read about diamond cutting, the more I am convinced that it must be an EXTREMELY STRESSFUL job.

I sure hope diamond cutters are well paid!

Lynn

 

[perry]

Been gone for most of the last 2 weeks.

Concerning how stressfull the job is...

I suspect that for the artist it is not stressfull, but constantly chanllenging with a huge emotional payoff when a stone comes out well.

The "good mechanic" is probably somewhat bored by the process.

Only those who have difficulty cutting or controling the machines on a routine basis are probably under a lot of stress.

That is how many other professions seem to work where people can really impact the end result.

Perry

 

[Paul-Antwerp]

On another note, Jonathan,

Have you noticed in these charts, that sometimes an area of 0 borders to an area of 2 or even 3. And did you notice at the same time, that this happens to be in combos that we personally both like very much.

It reminds me of the studies of Bruce Harding, who noticed that in all gemstones, the best possible combinations were always close to a no-go-area.

In such a combination, the scintillation should be stronger, because as soon as you start to rock your diamond, you have a stronger on-off-effect in the light windows (AGS-term) of that diamond.

On the other hand, it is very tricky to cut in that area, because that much lower grade is so damn close. Luckily, my cutters can stand the stress.

Live long,

 

[Rhino]

Date: 2/7/2005 10:43:44 AM
Author: Paul-Antwerp
On another note, Jonathan,

Have you noticed in these charts, that sometimes an area of 0 borders to an area of 2 or even 3. And did you notice at the same time, that this happens to be in combos that we personally both like very much.

It reminds me of the studies of Bruce Harding, who noticed that in all gemstones, the best possible combinations were always close to a no-go-area.

In such a combination, the scintillation should be stronger, because as soon as you start to rock your diamond, you have a stronger on-off-effect in the light windows (AGS-term) of that diamond.

On the other hand, it is very tricky to cut in that area, because that much lower grade is so damn close. Luckily, my cutters can stand the stress.

Live long,

LOL! Yes I did notice this! When you run along the 41 degree pavilion line (looking at 56 table chart) the only "0"s are for crown angles ranging from 33.6 - 34.2. ME LIKE. It is in a sense similar to HCA that gives stones hits once they hit the 41 degree pavilion zone. Not sure how HCA does with 41 angles coupled with shallower crowns though.

Ok... just ran a 41 with a 34 and gets a 1.3. 34.4/41 gets a 1.6 while this takes a hit from "0" to "1" on the AGS scale. Bring that pavilion angle down just .1 degree and you''re back in the cherry zone. I really like what I see so far and thanks for forwarding Pete my email too btw. We''re having some interesting discussions.

I can see how it could be stressful cutting, especially when sites are posting images that show extraneous details on each stone.

Kind regrards,

 

[Rhino]

Also wanted to note one correction on the AGS scales too ...

The measurement of the lower girdles is not LG length but LG depth (as used in DiamCalc).

 

[RockDoc]

Hi Paul & Rhino

I should have my AGS disc shortly...

It''s really interesting how this has turned so dramatically...

I appreciate both your postings, and the research work you''ve done...

It is good to see what I was preaching about with the 40 Mystery facet stuff is coming to a much broader acceptance.

And it very encouraging that at least one of the major labs will grade taking these things into consideration. The switch to individual measuring of all the facets is necessary since the diamond ( round anyway ) has 57 of them.

The only "problem" I see with this is how much variance between each group of facets will become the standard and how it will affect the grading. Gonna be an interesting challenge for cutters to make each group equal.. maybe even impossible due to the hard side and soft side of the stone, and the ability for each facet to achieve a great polish.

I think the GIA is going to be facing some serious grading system decisions in the future.

It is really gonna interest me to see the results and how it will affect other labs,the selling trade, as well as the cutters and the equipment dealers.

Thanks Paul and Rhino - you''ve both made some really great postings.


Rockdoc

 

[RockDoc]

Paul & Rhino

As you all know I''ve been preaching about girdles being foundation of a well cut stone.

In Rhino''s first posting he mentions a 3.5% girdle....Since you two have the disc, and mine hasn''t arrived yet... what is your take on how significantly the girdle come into analysis.

The eightstars have incredibly cut girdles as well as very tight roundness specs. Has AGS done any comparative studies on the variations of the girdle?

Interesting to hear Paul''s opinion on how the girdle may affect light retrun on if either the GIA or AGS is paying attention to that.

When the final software comes out, by both major labs, it will be fascinating to see how they deal with this and what the differences are like in comparing them to each other.

Exciting stuff happening!

Rockdoc

 

[JohnQuixote]

The CD we received had nothing burned on it (maybe we got the ultra-duper secret version).

We requested another.

So - While we've got Rhino and Paul looking - Guys, I hope you don't mind a question...

I am encouraged by the discussions of minor facets. However, I hope AGS intends to be more precise than GIA. I know you're looking at cutting guidelines, but do either of you see any hints about how the minors will be measured incrementally? For instance, will they treat length (or depth) in conventional increments of 1% ?

We must hope they do not march in step with GIA's "ham-fisted" {-GH} approach and round to nearest 5% to make it more "manageable"... From reports, in GIA's system both illustrations I've attached would be considered 80% (lgf78% - lgf 82%).

 

[Paul-Antwerp]

Date: 2/9/2005 12:15

8 AM
Author: JohnQuixote
The CD we received had nothing burned on it (maybe we got the ultra-duper secret version).

We requested another.

So - While we''ve got Rhino and Paul looking - Guys, I hope you don''t mind a question...

I am encouraged by the discussions of minor facets. However, I hope AGS intends to be more precise than GIA. I know you''re looking at cutting guidelines, but do either of you see any hints about how the minors will be measured incrementally? For instance, will they treat length (or depth) in conventional increments of 1% ?

We must hope they do not march in step with GIA''s ''ham-fisted'' {-GH} approach and round to nearest 5% to make it more ''manageable''... From reports, in GIA''s system both illustrations I''ve attached would be considered 80% (lgf78% - lgf 82%).

My dear John,

You disappoint me. Apparently, you were not paying attention in my class last week, and you have not reviewed the lesson. I will have to repeat it again. You naughty boy.

The charts on the CD are the ''cutting guidelines''. The charts are made for lower girdles of 80% and stars of 50%. However, there is huge difference between the cutting guidelines, and the way that AGS will grade stones. It is essential to make and understand that distinction.

Cut-grading will be software-driven, in the following way. One starts with a Sarin- or Helium-measurement (possibly OGI). The resulting full 3D-scan of the stone is entered into the AGS-software, and this will give the grade based upon the actual 3D-image of the stone. This means that the actual position and angle of each facet will be part of the cut-grade, without any rounding whatsoever.

This also means that one cannot establish a cut-grade using the charts for cutting guidelines. One will need the AGS-software, and one will need to be able to take a full measurement of the stone. I suppose that AGS will soon release the necessary software.

This is also important for anyone selling stones with another lab''s report. Even with the full Sarin-measurement, one cannot deduct a sure and certain AGS-cut grade from the cutting guidelines.

The above material is essential, and you can count on it being an important question in the next exams.

Live long,

 

[Paul-Antwerp]

Date: 2/8/2005 11:46

2 PM
Author: RockDoc
Paul & Rhino

In Rhino''s first posting he mentions a 3.5% girdle....Since you two have the disc, and mine hasn''t arrived yet... what is your take on how significantly the girdle come into analysis.

The eightstars have incredibly cut girdles as well as very tight roundness specs. Has AGS done any comparative studies on the variations of the girdle?

Interesting to hear Paul''s opinion on how the girdle may affect light retrun on if either the GIA or AGS is paying attention to that.

When the final software comes out, by both major labs, it will be fascinating to see how they deal with this and what the differences are like in comparing them to each other.

Exciting stuff happening!

Rockdoc

Hi Rockdoc,

The AGS-disc contains a lot of information, but there has been considerably more information provided over the last months. As far as I know, this started with the AGS-presentations at the Moscow Cut Conference of last April, and there have been various speeches and presentations by Peter Yantzer over the last months.

Those, who have invested their time in this, know a lot more about the details of the upcoming system, and I am happy to have done my homework.

At this point in time, I am torn between two lovers, either informing the public, or not informing the competition. I think that I have already given a lot of information. What is important to remember is that in the end, the cut-grading will be software-driven, and the parameters of the cutting guidelines are only guidelines.

On the point of not over-informing the competition, you are now asking for some details, to which I am happy to know the details, but that I would like to keep to myself. I hope that you understand. After all, we now have a competitive advantage by very well understanding the details of the future grading, and it would be stupid to just give all of this away.

Live long,

 

[valeria101]

Date: 2/9/2005 12:15:8 AM
Author: JohnQuixote

From reports, in GIA''s system both illustrations I''ve attached would be considered 80% (lgf78% - lgf 82%).

I am affraid I''ll ask for some clarification again...

The picture aparently tells me that less than the 5% approximation admissible by GIA standard is enough to make the difference between H&A and not-quite H&A. Is either of the new cut grading standards (GIA and new AGS) attempting to grade H&A ?