Diamond Buying by the Numbers - Perspective.

[Todd Gray]

This is a rant, I can already feel the flames of Haites licking upon my boot heels, but hopefully it will evolve into a discussion which will provide insight into the inner realm of diamond buying as seen from the perspective of the industry and my friends here on PS who take time out of their daily lives to provide advice to diamond buying consumers who are often looking for a quick fix to their diamond buying dilemma.

Hardly a day passes by where I do not see multiple threads on RT where consumers ask "is this a good diamond?" and offer only the information provided on the lab report, here I made this stone up:

Lab: GIA
Measurements: 6.47 - 6.50 x 3.99 mm
Weight: 1.02
Total depth: 61.4%
Table diameter: 55%
Crown angle: 34.5 degrees
Pavilion angle: 40.8 degrees
Girdle: thin to medium, faceted
Culet: none
Polish & Symmetry: Excellent

Everything looks good at first glance, so many people will likely tell the customer "looks good!"

A few people will advise the customer to ask the seller for pictures of the diamond as seen through a Hearts & Arrows viewer, an Ideal Scope and an ASET... Then when the images are provided, if they look decent ("lots of red in the ASET, looks good!") then the customer will probably again be told "looks good" and sometimes this advice is fine, but other times I have to say as an experienced diamond buyer that I''m looking at part of the image and screaming "No, No, NO!" at my monitor, but I''m prohibited from saying anything because I''m a vendor and quite often the name of the other vendor has been mentioned in the thread, or the identity of the vendor could easily be identified by simply running a search for the diamond within the PS search engine (don''t bother with my example, once again, I made the stone up).

I''m going to be so bold as to take the probable unpopular position that the ASET not be used to "evaluate" diamonds which have not been graded by the AGS Laboratory on the Platinum grading platform, and the reason I''m going to do so is because when the AGS uses the ASET to evaluate a diamond for brightness, they do NOT do so from the single static view that is commonly relied upon here on PS to determine whether a diamond "looks good" or not - when the AGSL uses the ASET to evaluate diamonds, they do so using ray tracing which considers the diamond as seen from hundreds of different perspectives and the Light Performance grade is conclusive of the results of all of the data - not the single static view, which happens to show the diamond from the best possible vantage point! The ASET evaluation is distinctly different than that provided by an Ideal Scope or Hearts & Arrows viewer which are designed to view the diamond from a single static vantage point.

~~~~~~~~~~~~
Proportions: even my own preferred range of 59 - 61.8%; 53 - 58%; 34.3 - 34.8; 40.6 - 40.9; etc. etc. is ONLY the beginning... So much more is waiting for you down the rabbit hole.
~~~~~~~~~~~~

Many people who are new to PS might not be aware that the measurements for Crown & Pavilion angle as stated on the lab reports reflect the average of eight measurements taken per section... For this reason, it is important to advise consumers to obtain the individual measurements which the average is based upon and preferably a diagram from the Sarin | OGI | Helium machine used to measure the diamond to study "the flow" of the facets to determine where the High / Low measurements occur / transition and to what degree the cutter adjusted the facets as the diamond was cut... In other words, when you look at the kite shaped Bezel facets on the top of the stone, say the average of 34.5 degrees is based on a spread of 34.2 - 34.8 degrees, most people would agree that this is a pretty minimal spread and without seeing "the flow" of the facets, they might tell you that the diamond is "tight" and you might purchase the diamond. But if you also looked at the facet-by-facet diagram for the diamond, it might tell a different story... Let''s say that you''re looking at the diagram of the Crown as if it were the face of a clock (from left to right) and the measurements start with 34.2 | 34.3 | 34.4 | 34.5 | 34.6 | 34.7 | 34.8 | 34.3

What additional insight would this provide? Well besides the fact that the diagram looks pretty cool (and the 3D Sarin file looks even cooler than that!) it would tell you that the table of the cutting wheel was tilted slightly, Doh! AND it would tell you that the cutter had to make an adjustment to even things out on the last Bezel facet! And if you looked at the same diagram structure for the facets which make up the Pavilion angle and determined that it was also cut at a tilt and the cutter had to make additional adjustments, you might realize that a particular "ideal cut" diamond is not as "ideal" as you might want it to be... Hmmm, I wonder what the stone would look like if the crown and the pavilion sections were tilted in opposite directions? What? You say that it could never happen? Well, you do realize that the majority of diamonds are cut "piece-mail" with different cutters cutting different sections of the diamonds as dictated by their station, thus each cutter sets their own wheel and makes adjustments to the stone to complete his or her section based upon what "precision" or "problem" they are handed by the cutter who cut the section which preceded them... So yea, it can happen.

And then there are the diamonds that have the ''right'' average measurements, such as 34.5 crown angle offset by a pavilion angle of 40.8 degrees, but the crown angle has a spread from 33.5 to 35.5 degrees and the pavilion angle has a spread of 39.8 - 41.8 degrees and the crown facets read like this: 33.5 | 35.5 | 33.5 | 35.5 | 33.5 | 35.5 | 33.5 | 35.5 and I''m telling you, I''ve seen it! In fact, I rejected 40 of 40 "ideal cut" diamonds like this from one particular cutter a few years ago right before the AGS Laboratory changed the way they determine whether a diamond is "ideal cut" or not - and it was this type of cutting that caused the AGS Laboratory to change how they graded diamond cut quality - don''t take my word for it, call the lab!

So P-L-E-A-S-E look past the average numbers on the lab reports and look past the basic data provided for the high and low measurements and look at the actual structure of the diamond! That''s what experienced diamond buyers do... This is the type of information that is probably only important to the 5-6% of consumers who find themselves on PS, but it drives me nuts that I keep seeing people rubber stamp diamond quality based on such limited information.

~~~~~~~~~~~~
Inclusions:
~~~~~~~~~~~~

Even if the diamond has been carefully evaluated by the seller, as I and many other professionals here on PS do with every diamond that we sell, I firmly believe that it is the best interest of the customer to have the diamond evaluated by an independent appraiser of their choosing, because as sellers we represent ourselves and the interests of the companies which we represent and the independent appraisers represent the client and the interests of the client.

 

[Lorelei]

Date: 4/19/2010 2:29:37 PM
Author:Todd Gray
This is a rant, I can already feel the flames of Haites licking upon my boot heels, but hopefully it will evolve into a discussion which will provide insight into the inner realm of diamond buying as seen from the perspective of the industry and my friends here on PS who take time out of their daily lives to provide advice to diamond buying consumers who are often looking for a quick fix to their diamond buying dilemma.

Hardly a day passes by where I do not see multiple threads on RT where consumers ask 'is this a good diamond?' and offer only the information provided on the lab report, here I made this stone up:

Lab: GIA
Measurements: 6.47 - 6.50 x 3.99 mm
Weight: 1.02
Total depth: 61.4%
Table diameter: 55%
Crown angle: 34.5 degrees
Pavilion angle: 40.8 degrees
Girdle: thin to medium, faceted
Culet: none
Polish & Symmetry: Excellent

Everything looks good at first glance, so many people will likely tell the customer 'looks good!'

A few people will advise the customer to ask the seller for pictures of the diamond as seen through a Hearts & Arrows viewer, an Ideal Scope and an ASET... Then when the images are provided, if they look decent ('lots of red in the ASET, looks good!') then the customer will probably again be told 'looks good' and sometimes this advice is fine, but other times I have to say as an experienced diamond buyer that I'm looking at part of the image and screaming 'No, No, NO!' at my monitor, but I'm prohibited from saying anything because I'm a vendor and quite often the name of the other vendor has been mentioned in the thread, or the identity of the vendor could easily be identified by simply running a search for the diamond within the PS search engine (don't bother with my example, once again, I made the stone up).

I'm going to be so bold as to take the probable unpopular position that the ASET not be used to 'evaluate' diamonds which have not been graded by the AGS Laboratory on the Platinum grading platform, and the reason I'm going to do so is because when the AGS uses the ASET to evaluate a diamond for brightness, they do NOT do so from the single static view that is commonly relied upon here on PS to determine whether a diamond 'looks good' or not - when the AGSL uses the ASET to evaluate diamonds, they do so using ray tracing which considers the diamond as seen from hundreds of different perspectives and the Light Performance grade is conclusive of the results of all of the data - not the single static view, which happens to show the diamond from the best possible vantage point! The ASET evaluation is distinctly different than that provided by an Ideal Scope or Hearts & Arrows viewer which are designed to view the diamond from a single static vantage point.

~~~~~~~~~~~~
Proportions: even my own preferred range of 59 - 61.8%; 53 - 58%; 34.3 - 34.8; 40.6 - 40.9; etc. etc. is ONLY the beginning... So much more is waiting for you down the rabbit hole.
~~~~~~~~~~~~

Many people who are new to PS might not be aware that the measurements for Crown & Pavilion angle as stated on the lab reports reflect the average of eight measurements taken per section... For this reason, it is important to advise consumers to obtain the individual measurements which the average is based upon and preferably a diagram from the Sarin | OGI | Helium machine used to measure the diamond to study 'the flow' of the facets to determine where the High / Low measurements occur / transition and to what degree the cutter adjusted the facets as the diamond was cut... In other words, when you look at the kite shaped Bezel facets on the top of the stone, say the average of 34.5 degrees is based on a spread of 34.2 - 34.8 degrees, most people would agree that this is a pretty minimal spread and without seeing 'the flow' of the facets, they might tell you that the diamond is 'tight' and you might purchase the diamond. But if you also looked at the facet-by-facet diagram for the diamond, it might tell a different story... Let's say that you're looking at the diagram of the Crown as if it were the face of a clock (from left to right) and the measurements start with 34.2 | 34.3 | 34.4 | 34.5 | 34.6 | 34.7 | 34.8 | 34.3

What additional insight would this provide? Well besides the fact that the diagram looks pretty cool (and the 3D Sarin file looks even cooler than that!) it would tell you that the table of the cutting wheel was tilted slightly, Doh! AND it would tell you that the cutter had to make an adjustment to even things out on the last Bezel facet! And if you looked at the same diagram structure for the facets which make up the Pavilion angle and determined that it was also cut at a tilt and the cutter had to make additional adjustments, you might realize that a particular 'ideal cut' diamond is not as 'ideal' as you might want it to be... Hmmm, I wonder what the stone would look like if the crown and the pavilion sections were tilted in opposite directions? What? You say that it could never happen? Well, you do realize that the majority of diamonds are cut 'piece-mail' with different cutters cutting different sections of the diamonds as dictated by their station, thus each cutter sets their own wheel and makes adjustments to the stone to complete his or her section based upon what 'precision' or 'problem' they are handed by the cutter who cut the section which preceded them... So yea, it can happen.

And then there are the diamonds that have the 'right' average measurements, such as 34.5 crown angle offset by a pavilion angle of 40.8 degrees, but the crown angle has a spread from 33.5 to 35.5 degrees and the pavilion angle has a spread of 39.8 - 41.8 degrees and the crown facets read like this: 33.5 | 35.5 | 33.5 | 35.5 | 33.5 | 35.5 | 33.5 | 35.5 and I'm telling you, I've seen it! In fact, I rejected 40 of 40 'ideal cut' diamonds like this from one particular cutter a few years ago right before the AGS Laboratory changed the way they determine whether a diamond is 'ideal cut' or not - and it was this type of cutting that caused the AGS Laboratory to change how they graded diamond cut quality - don't take my word for it, call the lab!

So P-L-E-A-S-E look past the average numbers on the lab reports and look past the basic data provided for the high and low measurements and look at the actual structure of the diamond! That's what experienced diamond buyers do... This is the type of information that is probably only important to the 5-6% of consumers who find themselves on PS, but it drives me nuts that I keep seeing people rubber stamp diamond quality based on such limited information.

~~~~~~~~~~~~
Inclusions:
~~~~~~~~~~~~

Even if the diamond has been carefully evaluated by the seller, as I and many other professionals here on PS do with every diamond that we sell, I firmly believe that it is the best interest of the customer to have the diamond evaluated by an independent appraiser of their choosing, because as sellers we represent ourselves and the interests of the companies which we represent and the independent appraisers represent the client and the interests of the client.

Hi Todd!

I do see what you are saying and agree with much of it, I and some of the others also try to take into account most of the things you mention ( and many of the vendors do offer Sarin/ Helium scans and so on that we can work with) but as you know the majority of us are not experienced diamond buyers but consumers on a consumer forum trying to offer the best help we can, of course there is always room for improvement but we have real limitations in the advice we can give others and it is important for buyers to be aware of where any advice given is coming from. I tend to take a more conservative approach with many diamonds even ones with the measurements you used above as I have seen the various things that can go wrong with angle swings, rounding etc, but equally its difficult as there is the possibility that we could be putting buyers off diamonds which could be perfectly fine.

It is essential we grow and learn so we move in the right direction to help others here but the thing is that a consumer advisor has neither the tools, experience or expertise for the most part and we also have to try to help those that aren't necessarily looking for a top notch superideal but just want a decently cut diamond.

I completely agree with the appraisal aspect too but again all we can do is advise as usual that its up to the buyer's comfort level, that an independant appraisal is recommended but in the end some will and some won't.

 

[axiochris]

Hi Todd,

As one of the aforementioned rookie diamond buyers, i would like to say thanks. I thought i was close to making a decision but i think i will do more research based on your post.

 

[Paul-Antwerp]

Nice ''rant'', Todd, but you were still very mild.

When comparing a face-up photo of an ASET to the actual AGS-grade, the AGS-grade not only uses ASET over various degrees of tilt, but the AGS-grade also contains a fire-metric. This is important as the ASET-photo does not give any info on fire, and the AGSL cut-grade is basically the only lab assessing Fire in any way.

Talking about Fire and Scintillation, they are still relative black spots in the gemological study of diamonds and, as such, no online-tool can effectively predict how a diamond ''performs'' on that level.

In that sense, I really feel for the advising consumers on this board, having to work with limited information and limited tools, while many consumers requesting advice expect a definite and technical yes/no as if we were talking about a repeatable factory-production-item, like a phone, a car or stereo-equipment.

Live long,

 

[Karl_K]

Date: 4/20/2010 9:32:33 AM
Author: Paul-Antwerp
Nice 'rant', Todd, but you were still very mild.


When comparing a face-up photo of an ASET to the actual AGS-grade, the AGS-grade not only uses ASET over various degrees of tilt, but the AGS-grade also contains a fire-metric. This is important as the ASET-photo does not give any info on fire, and the AGSL cut-grade is basically the only lab assessing Fire in any way.


Talking about Fire and Scintillation, they are still relative black spots in the gemological study of diamonds and, as such, no online-tool can effectively predict how a diamond 'performs' on that level.


In that sense, I really feel for the advising consumers on this board, having to work with limited information and limited tools, while many consumers requesting advice expect a definite and technical yes/no as if we were talking about a repeatable factory-production-item, like a phone, a car or stereo-equipment.


Live long,

Hi Paul do you mind if I complain about using scan based images for grading diamonds that particularly with fancies have no bases in reality?
I love digital but it has some very serious faults of falling for garbage in/garbage out.
Which is why we use real images to determine if our diamonds are within my tolerances not scan based.

It is funny that your praising virtual and I am complaining about it, talk about role reversal.....
But when I have aprox. a dozen scans from 3 different brands of scanners and no 2 images created from those scans are the same it tends to make one not trust them much.
With rounds they can do an excellent job most of the time so I don't have a problem with rounds but with fancies there is a problem there.

 

[Karl_K]

Date: 4/19/2010 2:29:37 PM
Author:Todd Gray

Proportions: even my own preferred range of 59 - 61.8%; 53 - 58%; 34.3 - 34.8; 40.6 - 40.9; etc. etc. is ONLY the beginning... So much more is waiting for you down the rabbit hole.

Hey Todd I am with you in saying that what is in the averages is just as important as the averages but....

I cringe whenever anyone quotes your numbers as gospel which isn't your fault because you say it is YOUR preferred range but it is just as big a problem as everything you mentioned.

 

[Paul-Antwerp]

Date: 4/20/2010 10:02:43 AM
Author: Karl_K

Date: 4/20/2010 9:32:33 AM
Author: Paul-Antwerp
Nice ''rant'', Todd, but you were still very mild.


When comparing a face-up photo of an ASET to the actual AGS-grade, the AGS-grade not only uses ASET over various degrees of tilt, but the AGS-grade also contains a fire-metric. This is important as the ASET-photo does not give any info on fire, and the AGSL cut-grade is basically the only lab assessing Fire in any way.


Talking about Fire and Scintillation, they are still relative black spots in the gemological study of diamonds and, as such, no online-tool can effectively predict how a diamond ''performs'' on that level.


In that sense, I really feel for the advising consumers on this board, having to work with limited information and limited tools, while many consumers requesting advice expect a definite and technical yes/no as if we were talking about a repeatable factory-production-item, like a phone, a car or stereo-equipment.


Live long,

Hi Paul do you mind if I complain about using scan based images for grading diamonds that particularly with fancies have no bases in reality?
I love digital but it has some very serious faults of falling for garbage in/garbage out.
Which is why we use real images to determine if our diamonds are within my tolerances not scan based.

It is funny that your praising virtual and I am complaining about it, talk about role reversal.....
But when I have aprox. a dozen scans from 3 different brands of scanners and no 2 images created from those scans are the same it tends to make one not trust them much.
With rounds they can do an excellent job most of the time so I don''t have a problem with rounds but with fancies there is a problem there.

I do not mind your complaint, Karl, and I fully agree. As such, I am not praising the virtual here.

Luckily, our production is a far distance from the minimum-level of AGS-0, so even with a faulty scan of one of our stones, it still passes the mark. So, in that way, it is not a problem for us, and I do not think about it.
So, where I see the benefit of the grade including a lot of tilted scenarios and a fire-assessment, I consider the problem of faulty scans as unimportant, because they do not affect our product.

Does this make sense?

Live long,

 

[Regular Guy]

Date: 4/20/2010 9:32:33 AM
Author: Paul-Antwerp
Nice ''rant'', Todd, but you were still very mild.

When comparing a face-up photo of an ASET to the actual AGS-grade, the AGS-grade not only uses ASET over various degrees of tilt, but the AGS-grade also contains a fire-metric. This is important as the ASET-photo does not give any info on fire, and the AGSL cut-grade is basically the only lab assessing Fire in any way.

Sorry, I''m a pretty casual reader here. Where is it that AGS measures fire? How is it represented? And, based on a calculation of what, using what scoring method?

Thanks in advance.

 

[yssie]

It's the new members looking for the yea/nay on one diamond or another who don't know this, and they're the ones who are going to take those "guides" as gospel. The consumers who know better - well, know better.



Maybe a new policy - just don't say a word until they've read the tutorial, every page of it! So everyone fully understands why Garry's cut advisor, Lorelei's cheat sheet, an IS image.. are very helpful tools that should be used judiciously, allowing for manoeuvring. Knowing the limitations of the tools you're using is always good practice.

 

[Hest88]

I agree Todd...but I also have a dissenting view, which is why I sometimes tell consumers the easiest thing to do is choose their vendor first.

When a consumer come here, they are usually overwhelmed. Most are not technical geeks, and they''ve read just enough to understand that they need help but feel overwhelmed by the numbers and angles and acronyms and suggestions to get pictures using machinery they''ve never heard of. They come here to ask us to make the complicated simple for them, the same way another consumer will just turn to a trusted vendor. If we throw more requests for numbers at them, and ask them to go out and get MORE measurements, I can imagine many just throwing up their hands and running screaming to the nearest local jeweler. The truth is, for most consumers, what we provide for them is enough--especially for a RB. They don''t need a more objectively perfect stone. Neither they nor their friends are going to notice the difference, anyway, nor will they really care.

 

[Paul-Antwerp]

Date: 4/20/2010 12:20:32 PM
Author: Regular Guy

Date: 4/20/2010 9:32:33 AM
Author: Paul-Antwerp
Nice ''rant'', Todd, but you were still very mild.

When comparing a face-up photo of an ASET to the actual AGS-grade, the AGS-grade not only uses ASET over various degrees of tilt, but the AGS-grade also contains a fire-metric. This is important as the ASET-photo does not give any info on fire, and the AGSL cut-grade is basically the only lab assessing Fire in any way.

Sorry, I''m a pretty casual reader here. Where is it that AGS measures fire? How is it represented? And, based on a calculation of what, using what scoring method?

Thanks in advance.

The AGS Fire-metric is a part of their cut-grade, I do not know for how much it counts.

The metric measures potential fire of a stone, just like the ASET-system does for potential brightness. The metric itself is a complicated combination of reverse and forward ray-tracing.

I must say that I already saw the fire-metric explained two years ago, but only in last week''s AGS-presentation did I understand it. I am still struggling with all the consequences, but it seems to prove a lot of views that I already held intuitively.

Live long,

 

[oldminer]

Todd;

Would the hypothetical diamond you began the thread with actually get an Excellent symmetry grade with the amount of variation you later stated might be present in the crown angles? To me, this may be key to why a stone does NOT get Excellent when it initially appears a great potential candidate for a top grade. Maybe in this respect you have made an example of the further detail you feel needs to be understood by whoever buys a diamond "by the numbers", but is it possible you have used a bit of a stretch to make example work for your argument?

We all know there are many examples of diamonds being touted as "Ideal" when they are in reality near misses to accepted guidelines. You are totally right about rejecting phoney Ideal Cuts.

On another front, "Fire as a metric to grade the quality of a cut is a poor choice. It is always present in beautiful diamonds under certain lighting, such as store lights, because of the physics of light. The measurement of total light return is of far more importance and is the key variable. Fire is always going to be a component present in the total light return. The visibility of fire has so many further varaibles that is an unreliable metric and just another example of throwing data into the soup and finding the soup tastes good even if the metric itself did not change the taste, the outcome, one iota. You will never see a diamond without fire in jewelry store lighting. There may be more or less of it, but all well cut diamonds will display fire to some extent in lighting which fosters its occurence.

 

[Cehrabehra]

Date: 4/20/2010 9:32:33 AM
Author: Paul-Antwerp
Nice ''rant'', Todd, but you were still very mild.


When comparing a face-up photo of an ASET to the actual AGS-grade, the AGS-grade not only uses ASET over various degrees of tilt, but the AGS-grade also contains a fire-metric. This is important as the ASET-photo does not give any info on fire, and the AGSL cut-grade is basically the only lab assessing Fire in any way.


Talking about Fire and Scintillation, they are still relative black spots in the gemological study of diamonds and, as such, no online-tool can effectively predict how a diamond ''performs'' on that level.


In that sense, I really feel for the advising consumers on this board, having to work with limited information and limited tools, while many consumers requesting advice expect a definite and technical yes/no as if we were talking about a repeatable factory-production-item, like a phone, a car or stereo-equipment.


Live long,

I think for most people, even those who drift into this board for a short time, that''s exactly how they do see it Paul. I don''t think the average buyer wants to REALLY understand diamonds - they just want to know enough to be assured they''re getting a fantastic stone and not getting ripped off. I have a friend who is an audiophile and he would argue that not every stereo that comes off production is identical - but to the pedestrian stereo purchaser how much difference does that make? You want good quality - great quality even - and a reasonable price point. I bet there is a audio board out there where people analyze the nth degree of sound technology...

I think this thread is a good one for those who care, but do you think these differences are great enough (or the consumer is fooled enough) to make a big deal out of it to the general public?

 

[rak4me]

Todd Gray wrote: ... when the AGS uses the ASET to evaluate a diamond for brightness, they do NOT do so from the single static view that is commonly relied upon here on PS to determine whether a diamond "looks good" or not - when the AGSL uses the ASET to evaluate diamonds, they do so using ray tracing which considers the diamond as seen from hundreds of different perspectives and the Light Performance grade is conclusive of the results of all of the data - not the single static view, which happens to show the diamond from the best possible vantage point! The ASET evaluation is distinctly different than that provided by an Ideal Scope or Hearts & Arrows viewer which are designed to view the diamond from a single static vantage point.

That''s one thing I was wondering--what the difference was between an ASET image taken by the seller and the image printed on the Platinum AGS report. Please correct me if I''m wrong, but is Todd saying that the image on the AGS report is an amalgamation of the hundreds of perpsectives AGS analyzes? If that''s true, IMO that ASET image should carry more weight than the one taken from the single best perspective ... which, not surprisingly, usually looks pretty nice. Experts, would you also tend to focus more on the AGS report ASET than any single-image ASET that is provided?

Todd Gray wrote: So P-L-E-A-S-E look past the average numbers on the lab reports and look past the basic data provided for the high and low measurements and look at the actual structure of the diamond! That''s what experienced diamond buyers do... This is the type of information that is probably only important to the 5-6% of consumers who find themselves on PS, but it drives me nuts that I keep seeing people rubber stamp diamond quality based on such limited information.

I include myself in that 5-6%, and like many I''m sure, now I know that average crown and pavilion angles aren''t the whole story. In general, the closer/tighter the spread of the angles, the better. I can find the spread on Sarin reports, but the ones I''ve seen (namely, the Sarin reports on BGD) don''t list each specific angle. Should a buyer always try to get all of the angles, or if they find a tight spread (say, 34.5 to 34. 9 crown and 40.5 to 40.7 pavilion), is that pretty solid?

 

[Karl_K]

Date: 4/21/2010 10:35:46 AM
Author: rak4me
Todd Gray wrote: ... when the AGS uses the ASET to evaluate a diamond for brightness, they do NOT do so from the single static view that is commonly relied upon here on PS to determine whether a diamond ''looks good'' or not - when the AGSL uses the ASET to evaluate diamonds, they do so using ray tracing which considers the diamond as seen from hundreds of different perspectives and the Light Performance grade is conclusive of the results of all of the data - not the single static view, which happens to show the diamond from the best possible vantage point! The ASET evaluation is distinctly different than that provided by an Ideal Scope or Hearts & Arrows viewer which are designed to view the diamond from a single static vantage point.



That''s one thing I was wondering--what the difference was between an ASET image taken by the seller and the image printed on the Platinum AGS report. Please correct me if I''m wrong, but is Todd saying that the image on the AGS report is an amalgamation of the hundreds of perpsectives AGS analyzes? If that''s true, IMO that ASET image should carry more weight than the one taken from the single best perspective ... which, not surprisingly, usually looks pretty nice. Experts, would you also tend to focus more on the AGS report ASET than any single-image ASET that is provided?

no, The image on the report is a computer generated face up image from a scan that often has serious problems.
A properly taken real image ASET is much more accurate.

 

[Dancing Fire]

Date: 4/19/2010 2:29:37 PM
Author:Todd Gray

Many people who are new to PS might not be aware that the measurements for Crown & Pavilion angle as stated on the lab reports reflect the average of eight measurements taken per section... For this reason, it is important to advise consumers to obtain the individual measurements which the average is based upon and preferably a diagram from the Sarin | OGI | Helium machine used to measure the diamond to study ''the flow'' of the facets to determine where the High / Low measurements occur / transition and to what degree the cutter adjusted the facets as the diamond was cut... In other words, when you look at the kite shaped Bezel facets on the top of the stone, say the average of 34.5 degrees is based on a spread of 34.2 - 34.8 degrees, most people would agree that this is a pretty minimal spread and without seeing ''the flow'' of the facets, they might tell you that the diamond is ''tight'' and you might purchase the diamond. But if you also looked at the facet-by-facet diagram for the diamond, it might tell a different story... Let''s say that you''re looking at the diagram of the Crown as if it were the face of a clock (from left to right) and the measurements start with 34.2 | 34.3 | 34.4 | 34.5 | 34.6 | 34.7 | 34.8 | 34.3

And then there are the diamonds that have the ''right'' average measurements, such as 34.5 crown angle offset by a pavilion angle of 40.8 degrees, but the crown angle has a spread from 33.5 to 35.5 degrees and the pavilion angle has a spread of 39.8 - 41.8 degrees and the crown facets read like this: 33.5 | 35.5 | 33.5 | 35.5 | 33.5 | 35.5 | 33.5 | 35.5 and I''m telling you, I''ve seen it! In fact, I rejected 40 of 40 ''ideal cut'' diamonds like this from one particular cutter a few years ago right before the AGS Laboratory changed the way they determine whether a diamond is ''ideal cut'' or not - and it was this type of cutting that caused the AGS Laboratory to change how they graded diamond cut quality - don''t take my word for it, call the lab!

So P-L-E-A-S-E look past the average numbers on the lab reports and look past the basic data provided for the high and low measurements and look at the actual structure of the diamond! That''s what experienced diamond buyers do... This is the type of information that is probably only important to the 5-6% of consumers who find themselves on PS, but it drives me nuts that I keep seeing people rubber stamp diamond quality based on such limited information.

Todd...those are the reasons why i always ask to see a sarin or helium report on stones that i''m interested in

i wanted to be sure the stone is tightly cut.

but then where do we drawl the line? how wide of a variance should we tolerate?

i try to pick stones within .3'' between the high/low on both the crown and the pavil angles.

 

[Karl_K]

Date: 4/20/2010 11:20:27 AM
Author: Paul-Antwerp

I do not mind your complaint, Karl, and I fully agree. As such, I am not praising the virtual here.


Luckily, our production is a far distance from the minimum-level of AGS-0, so even with a faulty scan of one of our stones, it still passes the mark. So, in that way, it is not a problem for us, and I do not think about it.

So, where I see the benefit of the grade including a lot of tilted scenarios and a fire-assessment, I consider the problem of faulty scans as unimportant, because they do not affect our product.


Does this make sense?


Live long,

I get what your saying but I do not agree that it is not important.
When any system is used it is important to understand its limitations and its weaknesses.
Any lab cut grade is an opinion from the lab on what they think is best, some opinions are better than others.
With rounds and likely princess cuts the AGS system does a good job but it has its limitations.

That your diamonds are well in the safe zone and extremely well cut does not take away those limitations overall.
Buying a diamond based on just one data point is not a good thing so it has to be kept in perspective.

 

[Dancing Fire]

IMO...GIA/AGS should include a full Sarin on their lab reports.

 

[Todd Gray]

Apologies, I started this thread and then got pulled offline by personal family business...

As Paul noted, my "rant" merely scratches at the surface of the issue, but I also did not want to write much more of a book than I already opened the thread with because I figured it was already getting too long, but as indicated, I also hoped that this would turn into a discussion.

Lorelei, I am in full support of your suggestion that newbies to Price Scope read the tutorials in detail before posting to the forum, it would eliminate a good 90% of the "is this a good diamond?" proposals! But we all know that most people posting such questions are anxious for an answer because they are right in the middle of trying to make a decision and need help. Fortunately for them, the forum is filled with people such as yourself who devote countless hours of time (without compensation) to address their concerns.

Karl, I understand your concern about people quoting ''my preferred range'' as gospel, but it is a good starting place. On the page of our web site where my preferred range of proportions is stated, the next two paragraphs discuss how there are other combinations of proportions which ''may'' provide similar results... And I have often indicated this on PS as well. I do feel however that ''my preferred range'' is an excellent place for consumers to start with because (as a rather well known director of a prominent gemological laboratory said during a presentation last week) it represents the sweet spot in terms of proportions for a round brilliant ideal cut diamond (if the diamond is cut correctly with consistency). And yea baby, I was mentioned by name on that one! (Wink''s got video!)

Dave, I do not believe that I said that the GIA would grade the examples which I provided in terms of potential variances in how the crown and pavilion sections were fashioned would be graded by the GIA as excellent... I merely provided examples of faceting variations which I''ve witnessed in the past as potential issues that consumers should be aware of as a reason to look past the average measurements provided on the lab reports by obtaining a facet-by-facet proportions analysis from a Sarin | Helium | OGI machine. I believe that I indicated that the stair step effect of the 33.5 | 35.5 | 33.5 scenario was one of the reasons why the AGS changed their rating system in 2005.

For the record, I''m not trying to say that "Lab X" is better than "Lab Y" in terms of their cut grading system, what I am trying to establish for consumers is a reason to look past the averages stated on the lab reports and provide a few examples of what to look for - because it doesn''t do them (consumers) any good to ask for additional information, such as a 3D model of the diamond and/or a facet-by-facet report, if they don''t know what they''re looking at and what is good / bad, etc.

Dancing Fire, oh I do like the minimal range of variance that you''ve specified
The lower the amount of deviation (the official gemological term) between the high and low measurements, the better the potential for light return... In the real world, a deviation of 0.0 - 0.5 is probably realistic and as I recall, I''ve only seen 0.0 - 0.1 a few times and I think I hesitated to sell the stone.

OH! I would yell HURRAH from the rooftops if the gemological laboratories added a FULL proportions analysis to their lab reports! Oh yes, my diamond purist heart skipped a beat at that suggestion! Unfortunately the reaction from the diamond cutters would likely be a swift boycott of whatever laboratory employed that brilliant idea.

 

[Todd Gray]

Date: 4/21/2010 10:35:46 AM
Author: rak4me
Todd Gray wrote: ... when the AGS uses the ASET to evaluate a diamond for brightness, they do NOT do so from the single static view that is commonly relied upon here on PS to determine whether a diamond 'looks good' or not - when the AGSL uses the ASET to evaluate diamonds, they do so using ray tracing which considers the diamond as seen from hundreds of different perspectives and the Light Performance grade is conclusive of the results of all of the data - not the single static view, which happens to show the diamond from the best possible vantage point! The ASET evaluation is distinctly different than that provided by an Ideal Scope or Hearts & Arrows viewer which are designed to view the diamond from a single static vantage point.



That's one thing I was wondering--what the difference was between an ASET image taken by the seller and the image printed on the Platinum AGS report. Please correct me if I'm wrong, but is Todd saying that the image on the AGS report is an amalgamation of the hundreds of perpsectives AGS analyzes? If that's true, IMO that ASET image should carry more weight than the one taken from the single best perspective ... which, not surprisingly, usually looks pretty nice. Experts, would you also tend to focus more on the AGS report ASET than any single-image ASET that is provided?


Todd Gray wrote: So P-L-E-A-S-E look past the average numbers on the lab reports and look past the basic data provided for the high and low measurements and look at the actual structure of the diamond! That's what experienced diamond buyers do... This is the type of information that is probably only important to the 5-6% of consumers who find themselves on PS, but it drives me nuts that I keep seeing people rubber stamp diamond quality based on such limited information.



I include myself in that 5-6%, and like many I'm sure, now I know that average crown and pavilion angles aren't the whole story. In general, the closer/tighter the spread of the angles, the better. I can find the spread on Sarin reports, but the ones I've seen (namely, the Sarin reports on BGD) don't list each specific angle. Should a buyer always try to get all of the angles, or if they find a tight spread (say, 34.5 to 34. 9 crown and 40.5 to 40.7 pavilion), is that pretty solid?

I wanted to address these questions individually from my group response because it is a discussion all its own.

As Karl indicated, the ASET image which appears on the AGS Platinum Diamond Quality Document is a computerized rendition which is based on the numerical data collected from the diamond during the proportions scan. There will always be variations between what a diamond looks like as seen through an actual gemological tool, such as an ASET, Ideal Scope or Hearts & Arrows viewer and a computer generated rendering - so as Karl pointed out, there are times when the ASET image on the AGS DQD look kind of out of whack. Clearly a photograph of the actual diamond as seen through an actual ASET scope will always be more interesting.

However the point which I am trying to make in my original post, is that I do not think that consumers should be making a decision to purchase a diamond based on how it looks in the photograph provided of the diamond as seen from a single top down vantage point through an ASET scope - because it is an incomplete analysis of the diamond in comparison to the Light Performance analysis conducted by the AGS Laboratory in their ASET platform which considers the diamond from literally hundreds of vantage points. If I had to draw a correlation, it would be something like... the photograph that somebody posts of themselves on a dating site provides some insight into how they look, but if we ran the person through the AGS ASET platform, we'd be provided with a performance rating which is based on the person as seen from hundreds of vantage points... Oh boy, I can see where this is about to go, my apologies in advance.

With regards to whether I believe a consumer should request additional proportions data when the deviation between the high and low measurements for the crown / pavilion sections are minimal, the answer is yes. Because for the reason stated above where the cutter might have made an adjustment during the cutting process to finish the stone... Using the range for crown angle provided by Rak4Me of "34.5 to 34. 9" degrees, what if the flow of the facets went something like 34.5 | 34.9 | 34.8 | 34.7 | 34.9 | 34.8 | 34.7 | 34.9 | it might be something you would want to take into consideration?

While certain web sites may not publish the full proportions analysis on their web site, most of those who publish a proportions analysis of the diamond showing the range for the high / low measurements will be able to provide a more detailed analysis upon request.

By the way, I neglected to mention that people should also be looking at the consistency of things like the star and lower girdle facets as well... It's all part of the Big Picture.

 

[oldminer]

Could a diamond with the crown angles exactly in the order you just posted: "34.5 | 34.9 | 34.8 | 34.7 | 34.9 | 34.8 | 34.7 | 34.9 |" ever be given an "Excellent" symmetry grade by AGS and /or GIA? Could it happen only sometimes? Or, would such a range of angles eliminate Excellent possible grading nearly all the time? I don''t know the answer and would appreciate the advice. I''m not trying to be tricky or to prove anyone wrong....THANK YOU

 

[Regular Guy]

Date: 4/21/2010 6:26:31 AM
Author: Paul-Antwerp
The AGS Fire-metric is a part of their cut-grade, I do not know for how much it counts.

The metric measures potential fire of a stone, just like the ASET-system does for potential brightness. The metric itself is a complicated combination of reverse and forward ray-tracing.

I must say that I already saw the fire-metric explained two years ago, but only in last week''s AGS-presentation did I understand it. I am still struggling with all the consequences, but it seems to prove a lot of views that I already held intuitively.

Live long,

I suppose two data points of particular interest, from these comments, are both first & second hand from your observations.

Truly, it would be good to hear as first hand as possible how AGS measures fire.

However, as both our reporter in the field, and the person now bringing forward these observations/reflections, I (and maybe we?) would be interested in your personal thoughts on this, Paul.

For example, you HAVE been singularly (well, Rhino has been broadly critical, too, without providing the more detailed comments you have done) critical of the HCA''s intent to say anything purposive about fire and scintillation. Clearly, you here are supportive of AGS''s analysis.

I just went to Garry''s HCA site to see more of what he says about fire in particular. Octonus seems to be implicated...and although the material at this site (from Garry) is dated, and Octonus is in motion, I don''t know the extent to which any fundamentals on fire have been recalculated by Octonus or not. Consistent with Garry''s comments at his site, and with the HCA, are the idea that both crown height, and table size bring significant effects. It would be interesting to know what variance there is between these two analyses, at least from your point of view, if not from AGS.

I copy below what seems to be the pertinent info from Garry''s HCA site:

----------

It is commonly and correctly believed that diamonds with steeper crown angles and smaller tables have enhanced fire. Believing this makes objective observation based study of the nature undertaken here was somewhat difficult. However the discovery that shallow crown angled diamonds display enhanced fire challenged the preconditioning notion.

I acknowledge that fire is the most subjective and least reproducible of the four factors presented here. Never the less we have made many loosely structured comparisons with actual diamonds in various lighting conditions and a variety of observers.

The first of these two sets of charts show a selection of crown and pavilion proportion combinations with the virtual fire tool from the MSU / Octonus website www.cutstudy.com/cut/english/comp/scint1.htm. The second chart has had a head shadow effect subtracted.

Because HCA is concerned with the face up view, removal of the central section of the image effectively reproduces the potential for fire should a ray of light fall on the diamond from the same direction as one of these areas of a firey flash. Many people find this concept rather difficult to understand, and it is very difficult to explain. It may help to imagine that we are considering the ray of light to be going in the opposite direction. Therefore the more firey flashes on the imaginary screen, the more potential fire could be displayed. However we must always remember that excessive brilliance will drown out potential fire.

 

[Karl_K]

Date: 4/21/2010 12:46:22 PM
Author: oldminer
Could a diamond with the crown angles exactly in the order you just posted: '34.5 | 34.9 | 34.8 | 34.7 | 34.9 | 34.8 | 34.7 | 34.9 |' ever be given an 'Excellent' symmetry grade by AGS and /or GIA? Could it happen only sometimes? Or, would such a range of angles eliminate Excellent possible grading nearly all the time? I don't know the answer and would appreciate the advice. I'm not trying to be tricky or to prove anyone wrong....THANK YOU

Yes it could
That order is not uncommon.
There have been cases of much wider ranges getting EX/ID symmetry.

I wouldn't be concerned with such a group if the images looked good.

Sometimes a huge variation in angles is a tilted table which gets tricky and could get the new AGS0 with a scan that shows huge variations in angles.
This is far more complicated than x is good and y is bad.

edit: the more I think about it there is nothing wrong with that group.
Could be on a super-ideal h&a.

 

[Todd Gray]

Date: 4/21/2010 12:56:35 PM
Author: Karl_K

Date: 4/21/2010 12:46:22 PM

Author: oldminer

Could a diamond with the crown angles exactly in the order you just posted: ''34.5 | 34.9 | 34.8 | 34.7 | 34.9 | 34.8 | 34.7 | 34.9 |'' ever be given an ''Excellent'' symmetry grade by AGS and /or GIA? Could it happen only sometimes? Or, would such a range of angles eliminate Excellent possible grading nearly all the time? I don''t know the answer and would appreciate the advice. I''m not trying to be tricky or to prove anyone wrong....THANK YOU

Yes it could

That order is not uncommon.

There have been cases of much wider ranges getting EX/ID symmetry.

I wouldn''t be concerned with such a group if the images looked good.

Sometimes a huge variation in angles is a tilted table which gets tricky and could get the new AGS0 with a scan that shows huge variations in angles.

This is far more complicated than x is good and y is bad.

edit: the more I think about it there is nothing wrong with that group.

Could be on a super-ideal h&a.

"This is more complicated than x is good and y is bad" and that is exactly the point I am trying to get across with this thread... I''m truly happy with how well this has been received by the way

And Karl is correct, there is not anything necessarily wrong with the adjustment made to the cutter in the example provided above. But it ''might'' be an issue if the cutter who fashioned the pavilion also made such an adjustment in direct correlation to the lower crown angle measurement, something like this:

34.5 | 34.9 | 34.8 | 34.7 | 34.9 | 34.8 | 34.7 | 34.9 |
40.4 | 40.7 | 40.8 | 40.9 | 40.8 | 40.7 | 40.9 | 41.0 |

And I honestly don''t know whether such a diamond would warrant a top rating from either the AGS or the GIA because I don''t scrutinize their grading parameters as much as I stick to my own (because I buy to my own preferences and not lab specs)... so somebody else is going to have to address that part of the equation.

 

[oldminer]

Thanks for the advisory. Seems interesting, at least to me, that the symmetry we can measure objectively may have a noticeable range before the symmetry grade is lowered to the Very Good step. As a follow-up,. Are there a range of crown angles from high to low which would lower always the Symmetry grade from Ex to VG? Such grade setting points always are of interest although not the way anyone would suggest to select a diamond.

 

[Karl_K]

Date: 4/21/2010 1:36:32 PM
Author: oldminer
Thanks for the advisory. Seems interesting, at least to me, that the symmetry we can measure objectively may have a noticeable range before the symmetry grade is lowered to the Very Good step. As a follow-up,. Are there a range of crown angles from high to low which would lower always the Symmetry grade from Ex to VG? Such grade setting points always are of interest although not the way anyone would suggest to select a diamond.

At some point it becomes physically impossible to line them up at the ex level that varies by facet, is there a downgrade before that point?

 

[oldminer]

Karl, you answered my question with a question, although you seem to have made some sort of statement in the sentence not intended as a question. I am surely not the only one who can''t decipher your meaning.

Clearly, at some point the angles simply won''t work together and a cutter cannot make an excellent symmetry pattern. That''s logical of course. But, for EX to be the grade, do we really have to go as far as "it can''t be done"? I don''t think that is the point you wanted to make.

 

[Karl_K]

Date: 4/21/2010 3:21:37 PM
Author: oldminer
Karl, you answered my question with a question, although you seem to have made some sort of statement in the sentence not intended as a question. I am surely not the only one who can't decipher your meaning.


Clearly, at some point the angles simply won't work together and a cutter cannot make an excellent symmetry pattern. That's logical of course. But, for EX to be the grade, do we really have to go as far as 'it can't be done'? I don't think that is the point you wanted to make.

Sorry I wasn't clear,,
I don't know the answer either so was adding to your question.
There is a point where there is to much variation to line up everything to get the EX grade.
I don't know if they downgrade before then so was asking,,,

edit to clarify more: "I don't know if they downgrade before then if the cutter lines everything up."

 

[adamasgem]

Date: 4/21/2010 1:33:55 PM
Author: Todd Gray

Date: 4/21/2010 12:56:35 PM
Author: Karl_K

Date: 4/21/2010 12:46:22 PM

Author: oldminer

Could a diamond with the crown angles exactly in the order you just posted: ''34.5 | 34.9 | 34.8 | 34.7 | 34.9 | 34.8 | 34.7 | 34.9 |'' ever be given an ''Excellent'' symmetry grade by AGS and /or GIA? Could it happen only sometimes? Or, would such a range of angles eliminate Excellent possible grading nearly all the time? I don''t know the answer and would appreciate the advice. I''m not trying to be tricky or to prove anyone wrong....THANK YOU

Yes it could

That order is not uncommon.

There have been cases of much wider ranges getting EX/ID symmetry.

I wouldn''t be concerned with such a group if the images looked good.

Sometimes a huge variation in angles is a tilted table which gets tricky and could get the new AGS0 with a scan that shows huge variations in angles.

This is far more complicated than x is good and y is bad.

edit: the more I think about it there is nothing wrong with that group.

Could be on a super-ideal h&a.

''This is more complicated than x is good and y is bad'' and that is exactly the point I am trying to get across with this thread... I''m truly happy with how well this has been received by the way

And Karl is correct, there is not anything necessarily wrong with the adjustment made to the cutter in the example provided above. But it ''might'' be an issue if the cutter who fashioned the pavilion also made such an adjustment in direct correlation to the lower crown angle measurement, something like this:

34.5 | 34.9 | 34.8 | 34.7 | 34.9 | 34.8 | 34.7 | 34.9 |
40.4 | 40.7 | 40.8 | 40.9 | 40.8 | 40.7 | 40.9 | 41.0 |

And I honestly don''t know whether such a diamond would warrant a top rating from either the AGS or the GIA because I don''t scrutinize their grading parameters as much as I stick to my own (because I buy to my own preferences and not lab specs)... so somebody else is going to have to address that part of the equation.

Remember: What the measurements say, and what the measurements actually are, can be two different different things, for a variety of reasons. Even if the measurements were perfect, add the slightest noise, and the mathematical rounding alone can make the min -maxs be 0.1 different, so it could be 0.3 min-max just as easily as 0.5. And as you point out, you have to look at the stone to see the corresponding pavilion angles. The thin girdle does suggest the angle disparity on the crown angles, which still have the highest uncertainty in their measurements, I believe.

 

[ChunkyCushionLover]

Great thread Todd, got me thinking a bit about rounds and interpreting images again.

Couple of points:

1) The methodology used for grading disperion(there is no fire metric) in the AGS/PGS system and its foundations are found in this paper I didn''t purchase the PGS software or its supporting documentation so I don''t have the specific grading information. I would be interested to know specifically a lot of the fine details of the calculation for dispersion from those fire maps. Specifically for all the light performance categories I am interested to know how they weight each of the images. I read some time ago faceup was most heavily weighted then -5 degrees on each side is worth less, -10 on each side even less. I hope someone wouldn''t mind posting some of this for a lot of the catergories of PGS grading like Brightness and Dispersion or a link to it if its available somewhere.

2) I think what is lost in some threads is the nuances that are seen (in IS, ASET AND HA viewer) are being overlooked. They can tell us a lot about the stone without having to take a sarin and compare deviations in crown and pavillion angles.

i) "hotspots" showing areas of increased fire and scintillation
ii) what I call "rabbit ears" on the edge of the stone and their relaitve sizes showing variations in girdle thickness and painting and digging http://journal.pricescope.com/Articles/45/1/Visible-Effects-of-Painting--Digging-on-Superideal-Diamonds.aspx (images taken from here)
iii) different lengths of arrows showing assymetry and tilt from various factors in idealscope images
iv) hearts images (one heart differnt heart size, variation in heart brightness, size of heart cleft, seperation of heart from the arrows) and their implications of proper interpretation of imperfectly formed hearts, clefts , uneven brightness in the two halves of a heart etc. http://journal.pricescope.com/Articles/65/1/Hearts-and-Arrows-Diamonds-and-The-Basics-of-Diamond-Cutting.aspx
v) arrows images (arrow does not meet the girdle, variation in the lengths and thickness of the arrows etc.)

I am sure there are others nuances I may have missed and would welcome mention of these as well.

But there is also a problem if we are too critical and don''t realize how suttle some of these nuances are and how "near perfect" numbers or images also correlate to excellent performers in real life observation.
If we add enhanced layers of testing for things that may not even be seen by the average consumer, caution also needs to be taken that these critiques are put into proper context and that near top performing stones aren''t rejected for "mind clean" issues.