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Is this AGS Ideal cut diamond really not ideal?

RockBrat

Shiny_Rock
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Feb 22, 2016
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Hello! I am new here. I have done much research through these theads and have grown to have a huge appreciation of the community here and I wanted to be a part of it. I am on a diamond hunt and I have a question about a diamond. It is an AGS Ideal cut, graded in January 2016. But it seems off, am I missing something? Is this really an ideal cut diamond? Would it be a good performer or have lots of light leak?

2.01 ctw
Depth 61.6
Table 59.7
Crown angle 34.6 / 13.7%
Pavilion angle 41.3 / 43.7%
Pointed culet

When I plug it into the HCA tool I get a score of 4.6 good. I'm not sure what isn't adding up as I thought AGS Ideal cut diamonds were pretty reliably ideal.

I'd appreciate any thoughts on this, thank you!
 

tyty333

Super_Ideal_Rock
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Do you have any pictures of it? Not all ideal stones are the same. The pavilion is high on this one.
 

RockBrat

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No pictures unfortunately except for what little is shown on the cert. I can get pictures but essentially have to commit to a diamond and then get them done and return it within their 30 day timeframe if they're funky.

Thanks for your response! How would a high pavilion affect the diamond's brilliance?
 

tyty333

Super_Ideal_Rock
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22,663
It may have good enough light return to get an AGS0 but could be at the cost of fire. I would not order this stone unless I could
get images as well as a idealscope or aset. It would be interesting to see though.

Here is an AGS000 stone. I would not want it. It has funky angles too. Like I said, AGS000 stones are not all alike.
http://www.jamesallen.com/loose-diamonds/round-cut/2.01-carat-j-color-si1-clarity-ideal-cut-sku-564468

Check out this one... :knockout:
http://www.jamesallen.com/loose-diamonds/round-cut/2.09-carat-g-color-si1-clarity-ideal-cut-sku-476621
 

ChristineRose

Brilliant_Rock
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The HCA also claims that it is NOT a candidate for an AGS Ideal.

Also, AGS does not use the term "Ideal" although lots of people do use that. The AGS term would be 000.

I think there's got to be some sort of mix up here. Is there a certificate?
 

tyty333

Super_Ideal_Rock
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Messages
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ChristineRose|1456183105|3994164 said:
The HCA also claims that it is NOT a candidate for an AGS Ideal.

Also, AGS does not use the term "Ideal" although lots of people do use that. The AGS term would be 000.

I think there's got to be some sort of mix up here. Is there a certificate?
Um...ChristineRose...they put "Ideal" right on the grading report.
 

flyingpig

Ideal_Rock
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Pav/crown/table numbers are one of many considerations for the final cut grade. Diameter, star length and lower girdle height along with many others affects the final grade as well.

That AGS ideal boundary shown on the HCA graph gives some general idea, but not hightly accurate.

In addition, AGS grading is based on deduction in 9 different categories. 4 for light performance. 5 for others. Also symmetry and polish.

I dont fully understand, but there is more to consider than simply crown, pav and table numbers.

It is more helpful if the OP links the actual report, if the stone is on hold.
 

ADN

Shiny_Rock
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RockBrat|1456179216|3994138 said:
Hello! I am new here. I have done much research through these theads and have grown to have a huge appreciation of the community here and I wanted to be a part of it. I am on a diamond hunt and I have a question about a diamond. It is an AGS Ideal cut, graded in January 2016. But it seems off, am I missing something? Is this really an ideal cut diamond? Would it be a good performer or have lots of light leak?

2.01 ctw
Depth 61.6
Table 59.7
Crown angle 34.6 / 13.7%
Pavilion angle 41.3 / 43.7%
Pointed culet

When I plug it into the HCA tool I get a score of 4.6 good. I'm not sure what isn't adding up as I thought AGS Ideal cut diamonds were pretty reliably ideal.

I'd appreciate any thoughts on this, thank you!
Hi - - I'm in the trade and can't comment on this stone specifically, but in general, don't fool yourself into thinking that AGS 'Ideal' proportions are the end all be all. You can see quite a few examples of AGS ideal that are leaky and ugly. 'Ideal' (just like GIAs 'Excellent') is a range - just because it may be an AGS 'Ideal', this doesn't automatically put it above every other cut grade out there (or even amongst the best of the 'Ideal' cuts).
For example, AGS will give a cut grade of 'Ideal' for a stone with a 52% table / a 31% crown angle / a 41.8% pavilion angle - - I would think it's safe to say that most members here on PS would knock a stone like this back :) - - **note - these measurements entered into the HCA with a depth of 60 gets a 2.9...personally, I'm digg'n your specs much more than these... ;-)
I'm wondering if you might have thought that the AGS 'Ideal' grade automatically made it a 'super ideal' cut which is mentioned here on PS and by some retail sites? (*note - this is a retail/marketing term - it is not actually used by AGS as a grading term ;-) ).
You have to remember that the cut grade for AGS (just like every other grading lab) is based on a wide range of parameters - - - but just like a GIA cut grade of 'Excellent', it's about finding the balance between all of the parameters, and not just relying on one single metric.
Because there is not one single set of parameters that everyone can agree makes the most beautiful diamond, the range is meant to cover what most people consider aesthetically pleasing, and will have the best light performance - it is then up to you, after seeing the stone, to determine if you like the look of it or not.
Also, the HCA was developed with a preference for shallower stones, so a diamond with these angles would obviously not do well. The HCA favours shallow angled diamonds even if they don't make the GIA Excellent/AGS Ideal grade. This means that the HCA penalises many diamonds that have a perfectly normal spread for their carat weight based on their total depth. The HCA (by it's own admission) was designed to be an elimination tool, and clearly states it's limitations - so to consider it the be-all-end-all when buying diamonds is a bit naïve as there are so many other factors at play which determine a diamonds light performance.
Hope this helps
 

queradas

Rough_Rock
Joined
Jan 11, 2016
Messages
50
ADN|1456192858|3994234 said:
Hello! I am new here. I have done much research through these theads and have grown to have a huge appreciation of the community here and I wanted to be a part of it. I am on a diamond hunt and I have a question about a diamond. It is an AGS Ideal cut, graded in January 2016. But it seems off, am I missing something? Is this really an ideal cut diamond? Would it be a good performer or have lots of light leak?

It will be a decent performer and no it won't leak significantly, okay at a reduced price which is key! The AGSL Ideal LP designation is a significant measure and standard for Light Performance, even those on the edge of the cut grade are significantly well cut. This is a nuance that is often missed here by the 'Superideal' pushers. But being that this stone is on the edge of the AGSL cut grade it won't be the most impressive in terms of fire and it won't be the most balanced in terms of contrast and brilliance as compared to other CA/PA combinations but still not a dog.


2.01 ctw
Depth 61.6
Table 59.7
Crown angle 34.6 / 13.7%
Pavilion angle 41.3 / 43.7%
Pointed culet

When I plug it into the HCA tool I get a score of 4.6 good. I'm not sure what isn't adding up as I thought AGS Ideal cut diamonds were pretty reliably ideal.

The HCA is irrelevant, it uses averaged measurements of the some of the parameters, the AGSL 3D raytracing used in its cut grade of all facets trumps it everytime. Disregard the HCA when you have an AGSL platinum report.



I'd appreciate any thoughts on this, thank you!
Hi - - I'm in the trade and can't comment on this stone specifically, but in general, don't fool yourself into thinking that AGS 'Ideal' proportions are the end all be all. You can see quite a few examples of AGS ideal that are leaky and ugly. 'Ideal' (just like GIAs 'Excellent') is a range - just because it may be an AGS 'Ideal', this doesn't automatically put it above every other cut grade out there (or even amongst the best of the 'Ideal' cuts).

No idea what that means, what other cut grade is better? This stone is on the border of the AGSL cut grade it doesn't mean its a dog, its just not as good as other more balanced combinations in the bullseye of the AGSL range.

For example, AGS will give a cut grade of 'Ideal' for a stone with a 52% table / a 31% crown angle / a 41.8% pavilion angle

Crown and pavilion angles are measured in degrees not percentage points! 31 degrees CA and 41.8 PA.

You have to remember that the cut grade for AGS (just like every other grading lab) is based on a wide range of parameters - - - but just like a GIA cut grade of 'Excellent', it's about finding the balance between all of the parameters, and not just relying on one single metric.

The LP for AGSL isn't based on numerical parameters at all like GIAL! it is based on a modified dataset related to its 3D raytracing. It is far superior to any other grading metric, just because a stone has a 41.8 pavilion doesn't mean it can't be a bright and lively stone if it has a complimentary crown. A 31CA/41.8PA/60%T combination will never be the most balanced or brightest but can still have decent light return enough to get AGSL ideal grade for light performance (although its rare). The ideal grade requires decent brightness from edge to edge on the crown as well as limited obstruction and leakage.

- - I would think it's safe to say that most members here on PS would knock a stone like this back :) - - **note - these measurements entered into the HCA with a depth of 60 gets a 2.9...personally, I'm digg'n your specs much more than these... ;-)

AGSL cut grading does not grade by the "numbers" in its light performance grading it uses forward raytracing of how all the facets return light to the viewer from a Sarin scan of all facets of the actual diamond. Why would one use a rough chalk outline (averaged measurements of the Crown and Pavilion angles) of a stone to grade instead of accounting for every single facet with much more accuracy?

Also, the HCA was developed with a preference for shallower stones, so a diamond with these angles would obviously not do well. The HCA favours shallow angled diamonds even if they don't make the GIA Excellent/AGS Ideal grade. This means that the HCA penalises many diamonds that have a perfectly normal spread for their carat weight based on their total depth. The HCA (by it's own admission) was designed to be an elimination tool, and clearly states it's limitations - so to consider it the be-all-end-all when buying diamonds is a bit naïve as there are so many other factors at play which determine a diamonds light performance.
Hope this helps[/quote]
 

John P

Ideal_Rock
Trade
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Messages
3,563
RockBrat|1456179216|3994138 said:
Hello! I am new here. I have done much research through these theads and have grown to have a huge appreciation of the community here and I wanted to be a part of it. I am on a diamond hunt and I have a question about a diamond. It is an AGS Ideal cut, graded in January 2016. But it seems off, am I missing something? Is this really an ideal cut diamond? Would it be a good performer or have lots of light leak?

2.01 ctw
Depth 61.6
Table 59.7
Crown angle 34.6 / 13.7%
Pavilion angle 41.3 / 43.7%
Pointed culet
"AGS Ideal" includes a range of performance. Factually, this basic data set describes diamonds with with more light-loss through the pavilion than some other "AGS Ideal" and 0 combinations. More important to me, though, is what AGSL standard has been used to assign "Ideal" here?

The cut-guidelines AGSL issues to manufacturers for the Platinum Performance metric predict 60, 34.6, 41.3 combinations as candidates for AGS4 in performance (image below).

Here is an ASET simulating 60, 34.6, 41.3. Bear in mind this is a perfect wire-frame model of an 'imagined' diamond. Cut-consistency, minor facet choices, indexing and other variations all occur in actual/natural diamonds. Nevertheless, it may be interesting to see the essential starting-point for the primary data discussed in this thread.

So... Is it possible to improve (or de-improve) relative to the cut-guidelines?

Yes, if submitting for the Platinum Performance metric: Diamonds with deepish main-pavilion angles are improvable with smart lower-half choices relative to table size and creative indexing of the break facets. With that said, such tweaks would only move an AGS4 toward AGS3 or 2. And, in the interest of fair reporting, an actual diamond's performance may also go the other way.

Per all of the above: I believe the "AGS Ideal" diamond in this thread has been reported on the AGSL 2D proportions-report. Can the OP check on that and let us know?

When I plug it into the HCA tool I get a score of 4.6 good.
Right. The HCA and the AGSL Platinum cut-guidelines I posted both penalize the physical fact of light loss, mainly brightness reduction, for this combination.

I'm not sure what isn't adding up as I thought AGS Ideal cut diamonds were pretty reliably ideal.
Insert my first sentence here ;-)

I'd appreciate any thoughts on this, thank you!
I hope you find the general information interesting. Let us know of further developments.

ps-rockbrat-201-597-346-413-ags2005.jpg

ps-rockbrat-201-597-346-413-pwf-dc2005.jpg
 

Karl_K

Super_Ideal_Rock
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The biggest problem with these extreme borderline ags0 diamonds is slight measurement errors can take them from ags4-6 to borderline ags0. It would not be uncommon on multiple runs on the scanner or different scanners to get a 0 on one run and a 4-5 on another
The reason they get 0 is leakage is counted as contrast(I use it as such in my design in exchange for ~10% higher brightness overall so its not always bad) if the ratio of brightness and contrast is within the range it gets the grade.
However AGS does not take into account patterns and if they look good and a ring of leakage on an RB can create what is considered an unpleasant pattern to many.
But the biggest issue remains scanner accuracy when it comes to borderline cases.
 

queradas

Rough_Rock
Joined
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Messages
50
Karl_K|1456238841|3994395 said:
The reason they get 0 is leakage is counted as contrast(I use it as such in my design in exchange for ~10% higher brightness overall so its not always bad) if the ratio of brightness and contrast is within the range it gets the grade.
Karl,

We are getting into theoretical territory here as this is becoming less and less about the diamond posted by the OP and more and more about AGSL grading. I'd like to see the grading report before commenting further on OP's specific example as we would only be guessing at this point, assymetry in the angles might play a larger role than scan error.

I can't validate or refute John's claim that this might be an an old report using old AGSL's pre 2007 cut metrics which were 2d numerical and not based on their 3D ray tracing.

However I have no idea what you are writing here at it pertains to AGSL current deduction system for Round Brilliants.
You seem to be applying some subjective "concepts" for step cuts that do not apply to Round Brilliants or the way AGSL grades them.

For the Round Brilliant Cut grade there are separate deductions based on the modified and scaled dataset generated from a Sarin scan.

Final Cut grade = Maximum(Sum(Brightness ,Dispersion ,Contrast ,Leakage ,Weight Ratio, Durability ,Tilt), Girdle, Culet, Symmetry, Polish)

For both leakage(white in ASET 30) and contrast(blue in ASET 30) and brightness(RED in ASET30) and the rest of the criteria in brackets above the grading deductions are cumulative. The sum of the deductions are rounded. That means if the leakage deduction is 0.3 and the Brightness deduction is 0.11 and the Contrast deduction is 0.1 then the diamond will already not receive an AGSL ideal cut grade as it will be rounded up to 1. If the sum of all the deduction factors is greater than 0.5 it will not receive the 0(ideal) grade.
 

RockBrat

Shiny_Rock
Joined
Feb 22, 2016
Messages
116
Thank you so much to everyone who is posting here and all the great information! I am truly fascinated with trying to figure out this diamond and report. I am trying to post a picture of what I think is the 2D report, I'm not too familiar with AGS reports yet. It did get a 0 for light performance, proportion factors and finish but is that typical of all 0 cut grades under the old AGS system? Also, the date on the report is less than a month old. So if I'm understanding correctly, the angles are steep but the star length (or lower girdle length? ) can make up for the steep angles to still allow it to score an excellent grade?

I'm gaining so much knowledge!

Full info:
8.04-8.08x4.96mm
2.011 ctw
Table 59.7%
Crown angle 34.6
Crown height 13.7%
Girdle 2.2% to 4.5% faceted
Pavilion angle 41.3
Pavilion depth 43.7%
Star length 53%
Lower girdle length 78%
Total depth 61.6%
Culet pointed

20160223_093321-1.jpg
 

John P

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queradas|1456245684|3994451 said:
I can't validate or refute John's claim that this might be an an old report using old AGSL's pre 2007 cut metrics which were 2d numerical and not based on their 3D ray tracing.
Actually, I was considering the current reports AGSL offers which remain proportions-based. These 2D cutting-charts are more permissive, awarding "Ideal" for some diamonds unable or unlikely to get that grade if submitted for the 3D Platinum Performance report.

2D cut charts here
https://www.agslab.com/docs/pbcg/AGSLProportionCharts.pdf

Report Sample here
https://www.americangemsociety.org/ags-labs-gold-diamond-quality-report

After introducing the 3D metric in 2005, AGSL brought these 2D reports forward in 2008 for manufacturers seeking a more general metric emulating GIAs ease-of-predictability and use.
 

Karl_K

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queradas|1456245684|3994451 said:
Karl,

We are getting into theoretical territory here as this is becoming less and less about the diamond posted by the OP and more and more about AGSL grading. I'd like to see the grading report before commenting further on OP's specific example as we would only be guessing at this point, assymetry in the angles might play a larger role than scan error.
The question was about the ags grade and what factors can affect the grade are on point.
Sure there may be angle variations or may not be but I know for a fact that using the AGS software diamonds will move on the scale with different scans and even more so with different scanners when they are on the edge.
 

Karl_K

Super_Ideal_Rock
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queradas|1456245684|3994451 said:
For the Round Brilliant Cut grade there are separate deductions based on the modified and scaled dataset generated from a Sarin scan.

Final Cut grade = Maximum(Sum(Brightness ,Dispersion ,Contrast ,Leakage ,Weight Ratio, Durability ,Tilt), Girdle, Culet, Symmetry, Polish)
contrast is anything that causes contrast and leakage is counted.
You can take a design that has too little contrast in the AGS system and gets a 1 because of it and add leakage and get a 0.

The leakage deduction is a separate penalty.
 

RockBrat

Shiny_Rock
Joined
Feb 22, 2016
Messages
116
The report (or at least the only thing I have access to) is blue and called Diamond Quality Document. It shows the pic I posted and inclusion plotting and that's it. Plus a page that has all the numbers in a list format. So it seems there is more information in the reporting that I'm missing?
 

Texas Leaguer

Ideal_Rock
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RockBrat|1456249304|3994470 said:
The report (or at least the only thing I have access to) is blue and called Diamond Quality Document. It shows the pic I posted and inclusion plotting and that's it. Plus a page that has all the numbers in a list format. So it seems there is more information in the reporting that I'm missing?
If it says "light performance" on it, as you mentioned above, then it has been ray traced and is not one of the proportion based reports.
 

queradas

Rough_Rock
Joined
Jan 11, 2016
Messages
50
RockBrat|1456179216|3994138 said:
Hello! I am new here. I have done much research through these theads and have grown to have a huge appreciation of the community here and I wanted to be a part of it. I am on a diamond hunt and I have a question about a diamond. It is an AGS Ideal cut, graded in January 2016. But it seems off, am I missing something? Is this really an ideal cut diamond? Would it be a good performer or have lots of light leak?

2.01 ctw
Depth 61.6
Table 59.7
Crown angle 34.6 / 13.7%
Pavilion angle 41.3 / 43.7%
Pointed culet

When I plug it into the HCA tool I get a score of 4.6 good. I'm not sure what isn't adding up as I thought AGS Ideal cut diamonds were pretty reliably ideal.

I'd appreciate any thoughts on this, thank you!
Could you please post the report number I'd like to see the full report.
 

John P

Ideal_Rock
Trade
Joined
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Messages
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RockBrat|1456270178|3994636 said:
queradas|1456264153|3994583 said:
Could you please post the report number I'd like to see the full report.
AGS 104053899010
Thank you RockBrat, that is helpful.

It's an older report format. You can see it's sans-ASET, which is something of a drawback. Nevertheless in this case it has earned a light performance grade of 0.

http://www.agslab.com/pdf_sync_reports/104053899010-PDQDFK.PDF

I would really like to see the actual ASET for this diamond, and compare it to the simulation I posted above. Probably an interesting learning stone, in terms of what was done to improve the potential from AGS4 to AGS0.

Many thanks for the continued info!
 

RockBrat

Shiny_Rock
Joined
Feb 22, 2016
Messages
116
John Pollard|1456273984|3994669 said:
Thank you RockBrat, that is helpful.

It's an older report format. You can see it's sans-ASET, which is something of a drawback. Nevertheless in this case it has earned a light performance grade of 0.

http://www.agslab.com/pdf_sync_reports/104053899010-PDQDFK.PDF

I would really like to see the actual ASET for this diamond, and compare it to the simulation I posted above. Probably an interesting learning stone, in terms of what was done to improve the potential from AGS4 to AGS0.

Many thanks for the continued info!
Thank you for all of your help! And I really appreciated your simulation, it's awesome! I'm thinking of asking the vendor to order the stone for me because I'm curious and intrigued. They don't have a way to do an ASET there though but maybe it's a stone I have to see in person and figure out how to get an ASET of.

Maybe there is hope after all for all those GIA Excellent that so many people feel are not excellent. Lol!
 

kenny

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Good example of why I'd use AAAAAAALL the cut evaluation tools and only buy a round that does well on ALL of them.

Round is the most abundant diamond shape.
You can afford to be picky.
 

ChristineRose

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queradas3|1456457487|3995874 said:
The cut grading was still the 3D performance based grading based on the ray tracing. Diamond made AGS Ideal because of significant beneficial painting of the upper and lower halves which made this less of a "steep deep". The "ASET 33.5" image usually printed on the newer report formats would have been instructive.
So is the answer just ray tracing? Ray tracing is a much better cut predictor than the HCA, but you'd think actually measuring light performance would be even better. They had the physical diamond; why ray trace?
 

Texas Leaguer

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ChristineRose|1456505947|3996101 said:
queradas3|1456457487|3995874 said:
The cut grading was still the 3D performance based grading based on the ray tracing. Diamond made AGS Ideal because of significant beneficial painting of the upper and lower halves which made this less of a "steep deep". The "ASET 33.5" image usually printed on the newer report formats would have been instructive.
So is the answer just ray tracing? Ray tracing is a much better cut predictor than the HCA, but you'd think actually measuring light performance would be even better. They had the physical diamond; why ray trace?
This is an excellent question!
The AGS light performance cut grading system is purely based on mathematical calculation of light behavior which conforms to the laws of physics. In this way it can be an accurate and highly consistent means of analyzing cut quality. Within the theoretical construct of the ASET hemisphere, there are no external variables as are found in all physical/photographic staging setups and device designs. It also seperates color and clarity aspects from the pure analysis of cut quality. This approach also makes possible the use of the AGS software remotely such as is imbedded in Sarine and other scanning devices that create an accurate 3D model of the diamond.
 
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