Experts needed on Diamond Proportions.

[John P]

For exampe- take the rounding issue- which is clear cut advantage to AGSL for a physics guy or gal. But how much of an issue for someone wanting a good looking well cut diamond?
Put another way- say your cars speedometer was programmed for inches per hour versus miles per hour. The more precise measurement is clearly more accurate -but to what end?

If one leads to a crash, and the other doesn't - give me the more accurate speedometer.


These would display identical proportions-data on their GIA Reports except for girdle thickness (tn/med). For the record, AGS3 vs AGS1.

 

[teobdl]

That's a good example. But regardless, most would screen the windowed diamond out based on how thin the LGF's look, despite a report that says 80%. I don't think anyone is advocating trusting GIA measurements sight unseen, especially in margin situations that are prone to windows.

Re obstruction in the original proportions mentioned: doesn't the ASET you made show that obstruction may not be a problem in a real life diamond with those proportions? It needs to be evaluated by the end consumer.

 

[BrownyJones]

For a newbie like me who doesn't know much about diamonds but wants to make sure I get the best bang for my limited dollars on an ER, this is a very valuable discussion. I think I've narrowed it down to a couple of stones that are pretty close to superideal but are not at the level of a CBI or WF ACA. I'm trying to decide whether the additional dollars to get a superideal while sacrificing size and color would be worth it. One of the best advice a expert frequently gives is "pay for what you can see". I went to a couple of B&M stores this weekend to see whether I could see the difference between a superideal and GIA XXX. They didn't have any superideal (AGS 000) but had some GIA XXX of various specs. They all looked great, and it was difficult to see any difference in light performance. The stone with lower symmetry rating was definitely more dull than the others. Regardless, I'm still left with the same dilemma, which is whether to fork over more money for superideal. That's why I proposed an arbitrary scale for PSers to help me see the light, pardon the pun. It's in another thread.

[URL='https://www.pricescope.com/community/threads/and-its-down-to-these-2-advice-needed-please.210468/']https://www.pricescope.com/community/threads/and-its-down-to-these-2-advice-needed-please.210468/[/URL]

 

[John P]

That's a good example. But regardless, most would screen the windowed diamond out based on how thin the LGF's look, despite a report that says 80%.

I'm not sure I follow, teobdl? I'm addressing a comment about how relevant rounding is on GIA grading reports (see David's prior post). No one can see that on a grading report. It would require a photo or reflector image.

Re obstruction in the original proportions mentioned: doesn't the ASET you made show that obstruction may not be a problem in a real life diamond with those proportions? It needs to be evaluated by the end consumer.

Sure. As mentioned, I see topheavies with some frequency. They can be dynamite.

 

[John P]

I'm trying to decide whether the additional dollars to get a superideal while sacrificing size and color would be worth it. One of the best advice a expert frequently gives is "pay for what you can see".

Absolutely correct.

I went to a couple of B&M stores this weekend to see whether I could see the difference between a superideal and GIA XXX. They didn't have any superideal (AGS 000) but had some GIA XXX of various specs.

This goes-against the premise of your first sentence. It's like trying to decide if X wine is 'worth it' without ever tasting X wine. Also be aware that AGS 000 is not de-facto "super." That grade encompasses a variety of visual appearances - the subject diamond at the beginning of the thread potentially included. If you want to make an educated decision you'll need to find a way to taste all of the grapes, even if some are difficult to find - and the optimized cuts will be. They're in far smaller production.

 

[Rockdiamond]

John- to continue on with the speedometer analogy – is it possible that by giving too much information it might cause a crash? If someone does not understand how subtle some of these differences are they could overspend needlessly.

For a newbie like me who doesn't know much about diamonds but wants to make sure I get the best bang for my limited dollars on an ER, this is a very valuable discussion. I think I've narrowed it down to a couple of stones that are pretty close to superideal but are not at the level of a CBI or WF ACA. I'm trying to decide whether the additional dollars to get a superideal while sacrificing size and color would be worth it. One of the best advice a expert frequently gives is "pay for what you can see". I went to a couple of B&M stores this weekend to see whether I could see the difference between a superideal and GIA XXX. They didn't have any superideal (AGS 000) but had some GIA XXX of various specs. They all looked great, and it was difficult to see any difference in light performance. The stone with lower symmetry rating was definitely more dull than the others. Regardless, I'm still left with the same dilemma, which is whether to fork over more money for superideal. That's why I proposed an arbitrary scale for PSers to help me see the light, pardon the pun. It's in another thread.

[URL='https://www.pricescope.com/community/threads/and-its-down-to-these-2-advice-needed-please.210468/']https://www.pricescope.com/community/threads/and-its-down-to-these-2-advice-needed-please.210468/[/URL]

Hi Browny- thank you for adding a consumers input.
Question – you mentioned that you've narrowed it down to close to super ideal – how did you do so?
What I mean to say is : have you seen diamonds graded VG cut grade by GIA?
You mentioned that a diamond looked dull – and I do not doubt your assessment one bit. But what I will tell you is that it's very possible the dullness was not caused by symmetry

 

[denverappraiser]

I don't think anyone is advocating trusting GIA measurements sight unseen, especially in margin situations that are prone to windows.

Teobdl,

People ROUTINELY suggest accepting GIA's grades as gospel. At the consumer level that's the rule, not the exception. Even with a fair amount of the trade, the suggestion that there are some GIA-x's that are more excellent than others is received as blasphemy.

 

[Texas Leaguer]

That's a good example. But regardless, most would screen the windowed diamond out based on how thin the LGF's look, despite a report that says 80%. I don't think anyone is advocating trusting GIA measurements sight unseen, especially in margin situations that are prone to windows.

Re obstruction in the original proportions mentioned: doesn't the ASET you made show that obstruction may not be a problem in a real life diamond with those proportions? It needs to be evaluated by the end consumer.

It absolutely does need to be evaluated by the end consumer. As do all diamonds! Even if there was a perfect cut grading system that took into consideration stereo vision and all of the fascinating things we have learned and are constantly learning about perception driven by mysterious brain functions, you still need to see the diamond to verify in person that the stone is beautiful to your eye. If for no other reason than to make sure that other quality factors are not undermining performance.

I think one of the misconceptions here is that grading systems like GIA or AGS, or tools like HCA and reflector imaging, somehow replace the human eye as final arbiter of what is best for a particular consumer. In fact they all simply provide us information, some better some worse, and assist us in deciding which diamonds to focus our attention and our eyes on.

 

[John P]

John- to continue on with the speedometer analogy – is it possible that by giving too much information it might cause a crash? If someone does not understand how subtle some of these differences are they could overspend needlessly.

David, did you understand that these two diamonds would be reported identically on a GIA Report?


More importantly, do you believe this difference would be "subtle?"

 

[teobdl]

JP-sorry for the confusion. My point was that your argument against David isn't addressing his concern. You seem arguing that AGS is better because (among many other things) it allows one to discern between diamonds that otherwise would seem to be identical in the GIA system. David is principally arguing that AGS system is too finely diced and graded such that diamonds that are, in fact, beautiful are being unfairly regarded as duds.

 

[BrownyJones]

Hi JohnPollard, you are absolutely correct. That's why this is an interesting topic for me and also a tough decision. The more I learn about diamonds, the more I'm appreciating the finer details, just like a great cabernet. The problem is, as a wine tasting novice, I wouldn't drop 18k on my first bottle. But I'm hoping i never have to propose again - although there's a 50% I might have to if the divorce rate continues its trend - so two buck chuck is out of the question.

 

[Rockdiamond]

Thank you teobdl for helping to point out the problem.
John - do you see a lot of diamonds cut like the one on the left?
No one would need a reflector or cut grade to see that kind of difference.
I don't recall seeing a colorless stone that would produce an image like the one on the left.
That's not the subtle difference in speaking of.
No one is touching my other point- John or Neil -do you see many diamonds graded VG by GIA that are " off make"- iow badly cut?

Bryan - by eliminating stones sight unseen that may exhibit subtle differences we are encouraging consumers to buy blind ,- and at a higher price.

 

[John P]

JP-sorry for the confusion. My point was that your argument against David isn't addressing his concern. You seem arguing that AGS is better because (among many other things) it allows one to discern between diamonds that otherwise would seem to be identical in the GIA system.

No apologies needed Teobdl. I'm not arguing "against" people. I'm just a proponent of more precise and thorough reporting. David asked <<The more precise measurement is clearly more accurate -but to what end?>>... I showed to what end. Both of those diamonds would be reported identically. But in person they'd appear very differently.

David is principally arguing that AGS system is too finely diced and graded such that diamonds that are, in fact, beautiful are being unfairly regarded as duds.

Diamonds saying AGS3 or AGS4 on the report are very rare. They get sent elsewhere. So I'm not sure who/where they're being labeled as duds. Also, isn't it funny that this thread began with an opposite example? Gypsy identified a GIA VG which could potentially earn AGS 0. Hey now! Is this a case of "dud-reversal?"

I'd also comment on "too finely diced" in diamond-perspective: If we descend from D-E-F- and especially from FL-IF-VVS-VS those metrics are far more "finely diced" than any cut metric at any lab. If someone says "GIA E VVS1" that's pretty specific to me. But "EX" is not and even "Ideal" has such a range of appearances that I need more information.

Putting the rubber to the road: If someone asked me to select a diamond for my wife I could choose carat, color and clarity with high confidence based on the grading report. But I can't do that with cut, certain fluorescence levels or a few other factors. Thus, this is not just about cut. It's not about GIA and AGSL. As someone contributing and providing advice in the internet market I'm a proponent of more precise and thorough reporting. That's my position.

 

[John P]

Hi JohnPollard, you are absolutely correct. That's why this is an interesting topic for me and also a tough decision. The more I learn about diamonds, the more I'm appreciating the finer details, just like a great cabernet. The problem is, as a wine tasting novice, I wouldn't drop 18k on my first bottle. But I'm hoping i never have to propose again - although there's a 50% I might have to if the divorce rate continues its trend - so two buck chuck is out of the question.

Two buck chuck has its place! Maybe it's not the one you give your beloved on bended-knee, but chuck has been great for beach-time when I'm in the bay area.

 

[Texas Leaguer]

Thank you teobdl for helping to point out the problem.
John - do you see a lot of diamonds cut like the one on the left?
No one would need a reflector or cut grade to see that kind of difference.
I don't recall seeing a colorless stone that would produce an image like the one on the left.
That's not the subtle difference in speaking of.
No one is touching my other point- John or Neil -do you see many diamonds graded VG by GIA that are " off make"- iow badly cut?

Bryan - by eliminating stones sight unseen that may exhibit subtle differences we are encouraging consumers to buy blind ,- and at a higher price.

As usual RD, I could not disagree with you more.

By recommending the best available analysis on diamond cut quality we are helping consumers acquire information that better enables them to focus on the diamonds that they seek, out of hundreds of thousands of available candidates. The lowest price is not always the main driver for consumers looking for the most beautiful diamonds.

 

[Texas Leaguer]

JP-sorry for the confusion. My point was that your argument against David isn't addressing his concern. You seem arguing that AGS is better because (among many other things) it allows one to discern between diamonds that otherwise would seem to be identical in the GIA system. David is principally arguing that AGS system is too finely diced and graded such that diamonds that are, in fact, beautiful are being unfairly regarded as duds.

Teobdl,
I know that John has specifically responded to this post. Let me add my perspective. I do like his analogy about the highly diced color and clarity grades. To some consumers it matters whether a diamond is D or E or VVS 1 or VVS2. There is analysis available to help them find the stones they seek. For many consumers near colorless and eye-clean is good enough. For many the GIA cut grading system is granular enough to serve their purposes. For others the need to know more specifically about cut quality and light performance is a higher priority. For those customers AGSL reporting fills the need. Some customers want even more and for them super ideal is what they seek and they need even more diagnostics to find it.

If the consumer understands the strengths and limitations of the reports and diagnostic tools that are available, they can make educated decisions for themselves. We do not all want the same thing in wine, or cars or diamonds.

 

[Rockdiamond]

Bryan- Understanding the strengths and weaknesses of each system is exactly what I'm suggesting.
To achieve that goal we need to put the physicalcharacteristics in real terms as opposed to warning of obtuse concepts like leakage or obstruction.
You accuse me of not understanding the AGSL system yet when I raise valid points for discussion you can't or won't respond.
If you believe my points about Ray tracing are not valid, please explain why.
No one has answered my question about GIA VG cut grade stones.
I don't know what you do Bryan but my job invilves looking at and assessing diamonds every day.
Many- most- of the GIA VG's I see are quite attractive and take very close examination to see why they missed EX.
In fact there's a fair percentage that one really needs to look at the report to see why.
This compares to the higher clarities where it takes microscopic examination to grasp why a vs1 was not graded VVS2.
Nothing wrong with wanting a VVS- but there's something wrong with tradespeople leading consumers to believe they need to buy a VVS to get a beautiful diamond.
Or telling consumers how 'bad' a J color is.
If the consumer has never seen a J color, it's an "up-sell" plain and simple.
If folks are led to believe AGSL's admittedly more restrictive cut grade automatically means a better prettier diamond they are being up-sold.
This is not meant to be a put down of super ideal diamonds. Many will choose to spend the additional money on the AGSL stone upon inspection - but by no means all.
Just like the J color or the SI2

 

[Texas Leaguer]

Bryan- Understanding the strengths and weaknesses of each system is exactly what I'm suggesting.
To achieve that goal we need to put the physicalcharacteristics in real terms as opposed to warning of obtuse concepts like leakage or obstruction.
You accuse me of not understanding the AGSL system yet when I raise valid points for discussion you can't or won't respond.
If you believe my points about Ray tracing are not valid, please explain why.
No one has answered my question about GIA VG cut grade stones.
I don't know what you do Bryan but my job invilves looking at and assessing diamonds every day.
Many- most- of the GIA VG's I see are quite attractive and take very close examination to see why they missed EX.
In fact there's a fair percentage that one really needs to look at the report to see why.
This compares to the higher clarities where it takes microscopic examination to grasp why a vs1 was not graded VVS2.
Nothing wrong with wanting a VVS- but there's something wrong with tradespeople leading consumers to believe they need to buy a VVS to get a beautiful diamond.
Or telling consumers how 'bad' a J color is.
If the consumer has never seen a J color, it's an "up-sell" plain and simple.
If folks are led to believe AGSL's admittedly more restrictive cut grade automatically means a better prettier diamond they are being up-sold.
This is not meant to be a put down of super ideal diamonds. Many will choose to spend the additional money on the AGSL stone upon inspection - but by no means all.
Just like the J color or the SI2

David, I don't even know where to start with your laundry list here. I have little appetite for even responding for the following reasons:
1) I often don't understand your questions. The ones I do often look to me like statements in disguise.
2) I have attempted to answer your questions before, as others have, and it seems to be fruitless. You always seem to draw the thread into the same endless loop.
3) You do not seem to be seeking knowledge but rather to be making the same repetitive attacks on the value of cut quality analysis year after year.

To illustrate, I will attempt to respond to your various questions/statements:

Bryan- Understanding the strengths and weaknesses of each system is exactly what I'm suggesting. Good, we agree on something
To achieve that goal we need to put the physicalcharacteristics in real terms as opposed to warning of obtuse concepts like leakage or obstruction. "Warning of obtuse concepts like leakage and obstruction"? Really David? You can look up the concepts- they are real. And you should also look up obtuse while you are at it.
You accuse me of not understanding the AGSL system yet when I raise valid points for discussion you can't or won't respond. What valid points are you refering to?
If you believe my points about Ray tracing are not valid, please explain why. What points have you made about ray tracing?
No one has answered my question about GIA VG cut grade stones. What exactly is your question? If you read one of my original comments to Gypsy I advised that the proof of the putting on the VG stone in question would be if the customer thought it was beautiful.
I don't know what you do Bryan but my job invilves looking at and assessing diamonds every day. Congrats David. That is what all of us in the trade do for a living.
Many- most- of the GIA VG's I see are quite attractive and take very close examination to see why they missed EX.
In fact there's a fair percentage that one really needs to look at the report to see why. If you are saying there are top VGs that look very much like EX, that is not news. Cut grades are ranges on a continuum, like color grades and clarity grades.
This compares to the higher clarities where it takes microscopic examination to grasp why a vs1 was not graded VVS2.
Nothing wrong with wanting a VVS- but there's something wrong with tradespeople leading consumers to believe they need to buy a VVS to get a beautiful diamond. I don't see tradespeople doing that here.
Or telling consumers how 'bad' a J color is. I don't see that being done here either.
If the consumer has never seen a J color, it's an "up-sell" plain and simple. Forum members are not selling anything here. They are giving their personal opinions. It is part of the reason people come here. To ask others' opinions.
If folks are led to believe AGSL's admittedly more restrictive cut grade automatically means a better prettier diamond they are being up-sold.
This is not meant to be a put down of super ideal diamonds. Many will choose to spend the additional money on the AGSL stone upon inspection - but by no means all.
Just like the J color or the SI2 Nobody disputes this.

David, my intent is not to embarrass you. My intent is to illustrate why I do not feel inclined to respond to most of your questions. I am not avoiding anything except a waste of time for everyone.

 

[John P]

John - do you see a lot of diamonds cut like the one on the left?

Yes, in jewelry showrooms. Supplier lists are also full of them. To demonstrate, I grabbed these from the first page of a RapNet search: 0.50-3.00ct D-J, FL-VS2, 3EX 59 Table (307 total results), then simply matched 41PA, 35.5CA, etc.

Example 1, Example 2, Example 3

Every one of these diamonds could have the light return of either one of my simulations. That's the problem... Which of the above is more like the left? Which is more like the right? Are they somewhere in-between? There is no way to tell. In terms of light return they may look quite different from each other, yet their overall grade and even the reported angles are given as the same.

No one would need a reflector or cut grade to see that kind of difference.

Precisely. In actual viewing the left example would clearly be darker in many situations than the right example. But the report data isn't precise enough to know which example any of the subject diamonds resembles. I should also note that these sims are "best-case" scenarios, since they're perfect wire-frames and real diamonds won't be.

No one is touching my other point- John or Neil -do you see many diamonds graded VG by GIA that are " off make"- iow badly cut?

GIA disqualifies any diamond with pavilion-angle < 40.6 from being EX... I do indeed find appealing possibilities at that shallow end of GIA VG with better performance qualities than many steep-deep EX, as well as some AGS 0 outliers.

But the majority of VGs I see are deep. They tend to go quite dark at the edges and/or in the middle in normal lighting. Here's a classic example (credit to Garry Holloway). The stone on left is GIA EX/AGS 0. The stone on right is GIA VG.


In my workshops I use this as an illustration of how "one grade apart" in cut has far more visible implications than "one grade apart" in color or clarity.

Consequently, labels like 0 EX VG etc. mean less to me than actual diamond data and correlations to resulting appearance.

 

[John P]

...obtuse concepts like leakage or obstruction...

David, I would submit that these elements are no more obtuse than hue, tone and saturation used in color assessment - and size, position, nature and relief used in clarity assessment.

 

[denverappraiser]

Stones cut relatively recently, say within the last 30 years are, as a general rule, better optical performers than stones cut previously. Obviously, stones MINED recently are no different than stones mined 100 years ago. They're still just rocks. Largely this has to do with these grading scales. Consumers demand better optics and cutters deliver because they now sell better.

Cutters are not fools. They know these scales inside and out and there's roughly an inverse relationship between weight/yield and cut grade. The 'higher' the grade, the lighter the stone. To get the same money from the same piece of rough they need to sell at a higher per-carat price. This may seem obvious but it has not always been the case. Cut is king, but not too long ago it was size.

Why does it matter? The 'sweet spot' for many cutters is the demising line between VG and X. They know these scales inside and out and if all X's are viewed the same, the 'best' stone is the heaviest one that squeaks over that border. This is doubly true if it skates over an important weight boundary like 1.00 or 2.00. Sweet spot #2 is just over the G/VG boundary, for the same reason. VG is still pretty good, right? That's why we see so many of the steep/deep sorts of goods coming out of the big manufacturers. It's raised the bottom level of optical cut quality, but it's also lowered the top. The span from the top of X to the bottom of VG is enormous and encompasses a great variety of goods. It's far more than 2 grades on any of their other scales and it includes nearly the entire marketplace of modern round brilliants.

 

[Texas Leaguer]

Stones cut relatively recently, say within the last 30 years are, as a general rule, better optical performers than stones cut previously. Obviously, stones MINED recently are no different than stones mined 100 years ago. They're still just rocks. Largely this has to do with these grading scales. Consumers demand better optics and cutters deliver because they now sell better.

Cutters are not fools. They know these scales inside and out and there's roughly an inverse relationship between weight/yield and cut grade. The 'higher' the grade, the lighter the stone. To get the same money from the same piece of rough they need to sell at a higher per-carat price. This may seem obvious but it has not always been the case. Cut is king, but not too long ago it was size.

Why does it matter? The 'sweet spot' for many cutters is the demising line between VG and X. They know these scales inside and out and if all X's are viewed the same, the 'best' stone is the heaviest one that squeaks over that border. This is doubly true if it skates over an important weight boundary like 1.00 or 2.00. Sweet spot #2 is just over the G/VG boundary, for the same reason. VG is still pretty good, right? That's why we see so many of the steep/deep sorts of goods coming out of the big manufacturers. It's raised the bottom level of optical cut quality, but it's also lowered the top. The span from the top of X to the bottom of VG is enormous and encompasses a great variety of goods. It's far more than 2 grades on any of their other scales and it includes nearly the entire marketplace of modern round brilliants.

Neil, I agree with your assessment and it is informative for consumers to know how the market is shaped by developments such as the advent of new technologies, tools and grading standards. I would ague that the "quantum leap" has come within the last 10 years and coincides with the release of the GIA cut grade system. This is the moment when manufacturers started to have an incentive to improve their cutting for the broad market.

It is true that there were people advocating the importance of cut quality going back 100 years. But the main market force was always the manufacturers' calculus of deriving maximum dollars from a given piece of rough by maximizing weight retention while cutting it just well enough to be saleable. In the absence of widespread consumer knowlege about cut craftsmanship and its impacts on diamond beauty, and especially without a credible grading standard in place,there was little incentive (or penalty) for operating any other way.

That did start to change as you say some 30 years ago as more people took an interest in cut quality. It was accelerated by the establishment of the AGS Laboratory specializing in reporting on cut quality. But the sea change came when the big dog joined the party (GIA). The end result is a much greater number of well cut round diamonds for consumers to choose from.

Now if GIA would just roll out a cut grade system for fancy cuts (as they have said they will do) the market would continue to improve in the direction of the consumer.

Yes, the GIA system is broad and encourages cutting to the lower range of Ex. But with increasing interest in cut quality, there will continue to be a market for elite cutting. But until manufacturers are given a reason to revise their economic calculus on fancies, mediocrity will continue to prevail on that side of the market.

 

[Serg]

John - do you see a lot of diamonds cut like the one on the left?

Yes, in jewelry showrooms. Supplier lists are also full of them. To demonstrate, I grabbed these from the first page of a RapNet search: 0.50-3.00ct D-J, FL-VS2, 3EX 59 Table (307 total results), then simply matched 41PA, 35.5CA, etc.

Example 1, Example 2, Example 3

Every one of these diamonds could have the light return of either one of my simulations. That's the problem... Which of the above is more like the left? Which is more like the right? Are they somewhere in-between? There is no way to tell. In terms of light return they may look quite different from each other, yet their overall grade and even the reported angles are given as the same.

No one would need a reflector or cut grade to see that kind of difference.

Precisely. In actual viewing the left example would clearly be darker in many situations than the right example. But the report data isn't precise enough to know which example any of the subject diamonds resembles. I should also note that these sims are "best-case" scenarios, since they're perfect wire-frames and real diamonds won't be.

No one is touching my other point- John or Neil -do you see many diamonds graded VG by GIA that are " off make"- iow badly cut?

GIA disqualifies any diamond with pavilion-angle < 40.6 from being EX... I do indeed find appealing possibilities at that shallow end of GIA VG with better performance qualities than many steep-deep EX, as well as some AGS 0 outliers.

But the majority of VGs I see are deep. They tend to go quite dark at the edges and/or in the middle in normal lighting. Here's a classic example (credit to Garry Holloway). The stone on left is GIA EX/AGS 0. The stone on right is GIA VG.


In my workshops I use this as an illustration of how "one grade apart" in cut has far more visible implications than "one grade apart" in color or clarity.

Consequently, labels like 0 EX VG etc. mean less to me than actual diamond data and correlations to resulting appearance.

1)exactly same problem consumers have with Clarity grade.
take two SI2 diamonds. one can be on boundary SI1/SI2, other is SI2/I1
This is huge difference and usually it is invisible just from report .
from my point of view It is even more critical problem than roundness for cut parameters
2) How is about Milkiness ?
3) etc, etc

 

[Rockdiamond]

John - do you see a lot of diamonds cut like the one on the left?

Yes, in jewelry showrooms. Supplier lists are also full of them. To demonstrate, I grabbed these from the first page of a RapNet search: 0.50-3.00ct D-J, FL-VS2, 3EX 59 Table (307 total results), then simply matched 41PA, 35.5CA, etc.

Example 1, Example 2, Example 3

Every one of these diamonds could have the light return of either one of my simulations. That's the problem... Which of the above is more like the left? Which is more like the right? Are they somewhere in-between? There is no way to tell. In terms of light return they may look quite different from each other, yet their overall grade and even the reported angles are given as the same.

No one would need a reflector or cut grade to see that kind of difference.

Precisely. In actual viewing the left example would clearly be darker in many situations than the right example. But the report data isn't precise enough to know which example any of the subject diamonds resembles. I should also note that these sims are "best-case" scenarios, since they're perfect wire-frames and real diamonds won't be.

No one is touching my other point- John or Neil -do you see many diamonds graded VG by GIA that are " off make"- iow badly cut?

GIA disqualifies any diamond with pavilion-angle < 40.6 from being EX... I do indeed find appealing possibilities at that shallow end of GIA VG with better performance qualities than many steep-deep EX, as well as some AGS 0 outliers.

But the majority of VGs I see are deep. They tend to go quite dark at the edges and/or in the middle in normal lighting. Here's a classic example (credit to Garry Holloway). The stone on left is GIA EX/AGS 0. The stone on right is GIA VG.


In my workshops I use this as an illustration of how "one grade apart" in cut has far more visible implications than "one grade apart" in color or clarity.

Consequently, labels like 0 EX VG etc. mean less to me than actual diamond data and correlations to resulting appearance.

This is a very interesting discussion-
John- we are kind of saying the same thing, but differently. We agree that each stone needs to be evaluated physically, but I include more different styles and proportion sets in my consideration. For example, I will not eliminate a stone simply because it's VG as opposed to EX cut grade.
My question about VG cut graded stones, that you or others have seen in person was asked in earnest- I really am interested in your experiences and others, in this regard.
My experience in on the NYC market. I am most commonly looking at VG graded stones larger than 2cts - and/or stones that are lower colors, but not making the FLY grade, thereby eliminating the cut grade.
In that context, I don't see may VG cut graded stones that show a visual deficiency.
I don't know in which showrooms you've seen really badly cut round diamonds.....but my experience that in round diamonds, the state of cutting at the bottom has risen so much that finding clearly "off make" rounds is not all that easy- and certainly not in better retail stores.
Just my experince.


In terms of the images you've posted John- all due respect, but neither is in any way informative.
The wire frame images require a lot of extrapolation- what dos that diamond actually look like?
The shot of the two diamonds in a box provides no useful data IMO.
Lets remember that the state of the art in internet representation of diamonds has come quite along way in the last five years.
How many people are buying today without some sort of photograph?
Very few compared to just a few years back.
The wire frame image: if we could see what the diamond on the left looked like in reality, I believe it would be quite easy to eliminate it as a contender- regardless of the cut grade.
"Steep Deep" is a phrase used here on PS- and just about nowhere else.
Again, many of the differences we are discussing are incredibly subtle in a visual sense ( unlike the wire frame image)- when you actually look at the diamond.

The reason I used the word "obtuse" to describe leakage and obstruction is that I disagree that leakage in a round diamond is as easy to illustrate as color or clarity characteristics.

 

[Rockdiamond]

Stones cut relatively recently, say within the last 30 years are, as a general rule, better optical performers than stones cut previously. Obviously, stones MINED recently are no different than stones mined 100 years ago. They're still just rocks. Largely this has to do with these grading scales. Consumers demand better optics and cutters deliver because they now sell better.

Cutters are not fools. They know these scales inside and out and there's roughly an inverse relationship between weight/yield and cut grade. The 'higher' the grade, the lighter the stone. To get the same money from the same piece of rough they need to sell at a higher per-carat price. This may seem obvious but it has not always been the case. Cut is king, but not too long ago it was size.

Why does it matter? The 'sweet spot' for many cutters is the demising line between VG and X. They know these scales inside and out and if all X's are viewed the same, the 'best' stone is the heaviest one that squeaks over that border. This is doubly true if it skates over an important weight boundary like 1.00 or 2.00. Sweet spot #2 is just over the G/VG boundary, for the same reason. VG is still pretty good, right? That's why we see so many of the steep/deep sorts of goods coming out of the big manufacturers. It's raised the bottom level of optical cut quality, but it's also lowered the top. The span from the top of X to the bottom of VG is enormous and encompasses a great variety of goods. It's far more than 2 grades on any of their other scales and it includes nearly the entire marketplace of modern round brilliants.

I agree with much of what you wrote Neil.
On average it costs weight to cut to AGSL 000 proportions and finish- and there's also an increased labor cost.
That does make a GIA EX cut grade more attractive to cutters in some cases ( it really depend on the shape of the rough)
But remember that part of this equation gets the consumer a lower price on the GIA EX as compared to the AGSL000
In a competitive market like diamonds, the savings do get passed along to the consumer to make the goods more sale-able.
This is a large part of my argument against the blind mantra "Cut is King".
Sometimes consumers are better served sacrificing some cut quality - and it also makes demonstrating what the visual deficiencies are very clearly, so they see what they are giving up, or gaining. What some see as deficiency, others see as benefit in terms of visual attributes

We also agree that VG is a wide mark, and the bottom of the grade includes some stones showing a obvious visual deficiencies.
But, again, what I notice is a general increase in cut quality- and a corresponding decrease in clearly off made stones on the market- so I don't see badly cut VG's often.

 

[Rockdiamond]

Bryan- Understanding the strengths and weaknesses of each system is exactly what I'm suggesting.
To achieve that goal we need to put the physicalcharacteristics in real terms as opposed to warning of obtuse concepts like leakage or obstruction.
You accuse me of not understanding the AGSL system yet when I raise valid points for discussion you can't or won't respond.
If you believe my points about Ray tracing are not valid, please explain why.
No one has answered my question about GIA VG cut grade stones.
I don't know what you do Bryan but my job invilves looking at and assessing diamonds every day.
Many- most- of the GIA VG's I see are quite attractive and take very close examination to see why they missed EX.
In fact there's a fair percentage that one really needs to look at the report to see why.
This compares to the higher clarities where it takes microscopic examination to grasp why a vs1 was not graded VVS2.
Nothing wrong with wanting a VVS- but there's something wrong with tradespeople leading consumers to believe they need to buy a VVS to get a beautiful diamond.
Or telling consumers how 'bad' a J color is.
If the consumer has never seen a J color, it's an "up-sell" plain and simple.
If folks are led to believe AGSL's admittedly more restrictive cut grade automatically means a better prettier diamond they are being up-sold.
This is not meant to be a put down of super ideal diamonds. Many will choose to spend the additional money on the AGSL stone upon inspection - but by no means all.
Just like the J color or the SI2

David, I don't even know where to start with your laundry list here. I have little appetite for even responding for the following reasons:
1) I often don't understand your questions. The ones I do often look to me like statements in disguise.
2) I have attempted to answer your questions before, as others have, and it seems to be fruitless. You always seem to draw the thread into the same endless loop.
3) You do not seem to be seeking knowledge but rather to be making the same repetitive attacks on the value of cut quality analysis year after year.

To illustrate, I will attempt to respond to your various questions/statements:

Bryan- Understanding the strengths and weaknesses of each system is exactly what I'm suggesting. Good, we agree on something
To achieve that goal we need to put the physicalcharacteristics in real terms as opposed to warning of obtuse concepts like leakage or obstruction. "Warning of obtuse concepts like leakage and obstruction"? Really David? You can look up the concepts- they are real. And you should also look up obtuse while you are at it. Can you see leakage in round VG or EX cut grade diamonds? It's quite easy to show a consumer what a carbon spot is- or to compare a D and a J to see the difference. Leakage and obstruction are far more difficult to illustrate to a consumer looking at an actual diamond.
You accuse me of not understanding the AGSL system yet when I raise valid points for discussion you can't or won't respond. What valid points are you refering to? I'm referring to the fact that the basis of ray tracing assumes a fix position for the light, and viewer. This is a weak point in diamond evaluation. It does not invalidate ray tracing, but may help in context to understand both strengths and weaknesses of the system.
If you believe my points about Ray tracing are not valid, please explain why. What points have you made about ray tracing?
No one has answered my question about GIA VG cut grade stones. What exactly is your question? If you read one of my original comments to Gypsy I advised that the proof of the putting on the VG stone in question would be if the customer thought it was beautiful. My question was a simple one- do you see a lot of obliviously badly cut GIA VG cut grade stones ( stones showing a clear cut and easily visible visual deficiency)
I don't know what you do Bryan but my job invilves looking at and assessing diamonds every day. Congrats David. That is what all of us in the trade do for a living. I honestly don't know if buying diamonds is part of your job- maybe you don't get to look at a lot of diamonds daily- many people in this trade do not assess diamonds on a daily basis
Many- most- of the GIA VG's I see are quite attractive and take very close examination to see why they missed EX.
In fact there's a fair percentage that one really needs to look at the report to see why. If you are saying there are top VGs that look very much like EX, that is not news. Cut grades are ranges on a continuum, like color grades and clarity grades.
This compares to the higher clarities where it takes microscopic examination to grasp why a vs1 was not graded VVS2.
Nothing wrong with wanting a VVS- but there's something wrong with tradespeople leading consumers to believe they need to buy a VVS to get a beautiful diamond. I don't see tradespeople doing that here.
Or telling consumers how 'bad' a J color is. I don't see that being done here either.
If the consumer has never seen a J color, it's an "up-sell" plain and simple. Forum members are not selling anything here. They are giving their personal opinions. It is part of the reason people come here. To ask others' opinions. But if a well meaning consumer/ member is just going off promotional info and does not understand the real life differences, their recommendation may be leading the person asking in the wrong direction. Unintentional up-sell. I watch the forum closely and this happens all too frequently.
If folks are led to believe AGSL's admittedly more restrictive cut grade automatically means a better prettier diamond they are being up-sold.
This is not meant to be a put down of super ideal diamonds. Many will choose to spend the additional money on the AGSL stone upon inspection - but by no means all.
Just like the J color or the SI2 Nobody disputes this.

David, my intent is not to embarrass you. My intent is to illustrate why I do not feel inclined to respond to most of your questions. I am not avoiding anything except a waste of time for everyone.

I don't see this at all as a waste of time Byran. Part of my participation involves seeking knowledge, and another part involves teaching.

 

[sarahb]

But if a well meaning consumer/ member is just going off promotional info and does not understand the real life differences, their recommendation may be leading the person asking in the wrong direction. Unintentional up-sell. I watch the forum closely and this happens all too frequently.

Could you please provide concrete evidence of members up selling off of 'promotional info'.

I personally don't see it that way, however--facts & evidence would help clarify.

 

[Rockdiamond]

HI Sarahb,
I used the term "unintentional upsell"- probably a poor choice of words, as no one recommending diamonds is actually selling.


If someone truly believes that the majority of VG cut grade diamonds don't perform well, then clearly it makes no sense to recommend checking out a VG cut grade candidate. There's no bad intention involved. If you believe that's the case its the right thing to recommend.
I am saying that I've seen quite a few VG cut grade stones which cost between 5-25% less that lacked little in visual appeal. If any.
I am not suggesting every buyer take this approach- I don't always follow it myself. I love to own AGSL 000's
But if I was advising someone looking to maximize size, or other factors on a budget, I suggest including GIA VG cut grade stones in their search. Or AGSL1

 

[teobdl]

But if a well meaning consumer/ member is just going off promotional info and does not understand the real life differences, their recommendation may be leading the person asking in the wrong direction. Unintentional up-sell. I watch the forum closely and this happens all too frequently.

Could you please provide concrete evidence of members up selling off of 'promotional info'.

I personally don't see it that way, however--facts & evidence would help clarify.

Sarahb- I'd guess that this happens in >50% of posts where people are looking for buying advice, maybe even >80%. There is this a strong suggestion that not buying a super ideal means the buyer is "sacrificing light performance" and the buyer will be making a huge mistake if they don't buy one. While it is true that the behavior of diamonds changes as one deviates from the Brian Gavin standard of hearts and arrows, the degree to which the deviation impacts beauty in real life is greatly, greatly exaggerated by many posters. It's incredibly frustrating to see, especially as someone who will sift through actual inventories of non-super ideals to find legitimately great diamonds at good prices that maximize a person's budget. What many posters do is simply pull up the super ideal sites, plug in a budget, and find the 3 diamonds that match the person's criteria. Easy as pie. The problem is that the diamond is often 10-15% lighter with lower color or clarity than an equivalently priced diamond that, in real life, will behave almost identically for 99.9% of people in probably 95% of all situations. No, those aren't real numbers, but I doubt many people would debate the point.

PSers are supposed to be the ones who can dig through the haystack to find the needle with ease, and here we are telling people to avoid the haystack and go right to the pin cushion with the curated, custom, but uniformly made needles. Some people advise that they go to the expensive pin cushion out of naivety, others do so out of laziness.

I get it that a lot of people want the most well-cut diamond they can buy. Those people should absolutely get super ideal diamonds. But many people are buying these super ideals not because they really want the most well-cut diamond ("top 1% of all diamonds!") but because there's a suggestion that diamonds at the 95-98th percentile look like crap.

I hope my post doesn't come across as hostile against super ideal vendors and associates. My gripe is with the people who are proxy upselling out of naivety or laziness.

 

[Dancing Fire]

[quote="teobdl|

PSers are supposed to be the ones who can dig through the haystack to find the needle with ease, and here we are telling people to avoid the haystack and go right to the pin cushion with the curated, custom, but uniformly made needles. Some people advise that they go to the expensive pin cushion out of naivety, others do so out of laziness.

I get it that a lot of people want the most well-cut diamond they can buy. Those people should absolutely get super ideal diamonds. But many people are buying these super ideals not because they really want the most well-cut diamond ("top 1% of all diamonds!") but because there's a suggestion that diamonds at the 95-98th percentile look like crap.

I hope my post doesn't come across as hostile against super ideal vendors and associates. My gripe is with the people who are proxy upselling out of naivety or laziness.[/quote]



IMO recommending top ideal cut stones are the safest bet. Why go on a wild goose chase? b/c shipping cost will add up real quick unless the buyer got lucky on the first stone. I will only browse sites with top cut in-house stones instead of going on a wild goose chase.