GIA tricked & cheated: +63% depth XXX diamonds

[sledge]

Can someone explain this in layman‘s terms?

If I have understood correctly, by adding the extra facet you create an additional angle that allows a cutter to hide more weight/depth without making the pavilion angle steeper.

And from what I'm gathering the facet isn't picked up in the girdle height measurement, nor the pavilion depth measurement. So when Facetware calcs cut grade it ignores the facet and sees it as 63 vs 64.9 in this case.

Is this about right @Garry H (Cut Nut) and @Karl_K?

If so I think a side view of the stone shows the issue more clearly. I tried to show the extra facet with a pink line. See how it provides a "ramp" of sorts to connect the pavilion and girdle. I'm sure this is exaggerated and it's hand sketched but maybe it conveys the point.

 

[Serg]

If I have understood correctly, by adding the extra facet you create an additional angle that allows a cutter to hide more weight/depth without making the pavilion angle steeper.

And from what I'm gathering the facet isn't picked up in the girdle height measurement, nor the pavilion depth measurement. So when Facetware calcs cut grade it ignores the facet and sees it as 63 vs 64.9 in this case.

Is this about right @Garry H (Cut Nut) and @Karl_K?

If so I think a side view of the stone shows the issue more clearly. I tried to show the extra facet with a pink line. See how it provides a "ramp" of sorts to connect the pavilion and girdle. I'm sure this is exaggerated and it's hand sketched but maybe it conveys the point.

No. The extra facets had been added to reduce a girdle thickness .
if girdle is too thick a diamond can not receive GIA Ex grade.
A Total height can not downgrade GIA EX to GIA VG.
It has not any sense to discuss a connection between total height and GIA EX grades. there is not such connection.

The GIA calculates a brilliant-cut diamond’s depth by adding together the height of the crown, the average thickness of the girdle and the depth of the pavilion. It expresses this as a percentage of the stone’s diameter, with 63% being the maximum permitted depth for an Excellent cut. A diamond that is too deep reflects light badly

I never saw such statements from GIA.

 

[diagem]

"The GIA calculates a brilliant-cut diamond’s depth by adding together the height of the crown, the average thickness of the girdle and the depth of the pavilion. It expresses this as a percentage of the stone’s diameter, with 63% being the maximum permitted depth for an Excellent cut. A diamond that is too deep reflects light badly

I never saw such statements from GIA."

Me too, I never actually saw a quote such as this on any GIA official informational, I also dont think a slight spread issue should downgrade LP potential (although in some instances it might).

On the other hand I do believe extra facets should depreciate the craftsmanship top grade.

 

[Rockdiamond]

Can someone explain this in layman‘s terms?

I totally get this sentiment.
Let’s do a Cliff notes
Basically :
The thread is about the fact that diamonds are being cut deeper, and still getting GIA EX cut grade. Then the technicalities that are allowing cutters to get away with this. That aspect is indeed, highly technical.
Like you, I really don’t find myself moved by that side of the discussion. One caveat is that I do feel that by aiming for 6.3mm, ( however they get there from a technical standpoint) it feels like “cheating” to me. Instead of cutting really nice “spready” .90-.99ct stones the majority of what we see are chubby 1.00ct stones.

Another very interesting and easIer to grasp debate is flaring up over how much “spread” ( the physical size) should be taken into calculating light performance.
Some feel that LP and spread are unrelated. That position feels that a 6.3mm round, if perfectly cut, should not be penalized for looking like a .95ct.
I don’t take that position. But some very well informed cutters participating seem to.

 

[Karl_K]

Some feel that LP and spread are unrelated. That position feels that a 6.3mm round, if perfectly cut, should not be penalized for looking like a .95ct.
I don’t take that position. But some very well informed cutters participating seem to.

I feel spread should be a separate score and not part of light performance.
That way if I want to for whatever reason pick a stone with less spread I still know the light performance.
For example some of the very high crown oec and mrb cuts I like and have seen some in person may have smaller spread which people should know but they should not be penalized in the light performance category for it.

 

[Rockdiamond]

I feel spread should be a separate score and not part of light performance.

And I totally "get" why you feel that way. In fact, after all these years, I completely understand the rationale.
I still, to this day, feel that this bias unfairly places "light performance" above all else.
The issue is that the term itself is ambiguous.
Put a well cut 6.5mm diamond that leaks a little under the table next to a super ideal 6.3mm diamond.
Show them to a bunch of observers, in a blind test.
Many will gravitate to the size advantage of the well cut 6.5mm.
So the issue becomes the fact that the discussion places "Light performance" way above spread. Part of the result is that we now have 1ct diamonds that are roughly 3% smaller in average spread as compared to 20 years ago.

 

[sledge]

No. The extra facets had been added to reduce a girdle thickness .
if girdle is too thick a diamond can not receive GIA Ex grade.
A Total height can not downgrade GIA EX to GIA VG.
It has not any sense to discuss a connection between total height and GIA EX grades. there is not such connection.

I think we may be saying the same thing, but in a different way. Below is a hand sketch of what I am thinking.

Assuming all other elements remain the same except the girdle thickness, then the pavilion angle would have to change, right? I tried to illustrate this with the red vs blue sketch.

The black sketch shows the extra facet (almost acting like a "star facet" in the side view, except on the pavilion). By adding that facet, you can keep the same pavilion angle of the thicker girdle diamond (blue) but get the advantage of a thinner girdle diamond (red).

I also dont think a slight spread issue should downgrade LP potential (although in some instances it might).

On the other hand I do believe extra facets should depreciate the craftsmanship top grade

I think the key word is slight spread. As I think you are eluding to, if you change too much then your proportions have to change and LP could then be affected, right?

I also agree about depreciating the top grade, and would add that it would be nice to see a note about it being a modified cut with extra facets.

Edited to Add:
Thank you @Garry H (Cut Nut) for posting some interesting topics like this one in the last week or so. It's the type of technical jargon I enjoy listening and (trying) to participate in as I am soaking in and learning.

 

[John P]

I did mention in an earlier post Sergey that one of the 3 stones i found had a video and I could not see any extra facets - yet these stones are still deeper than 63% which GIA have always claimed to be a magic cut quality downgrade number

1) Sorry, I do know anything about such GIA claim . Could you please give a link to such GIA statement? For my understanding GIA does not use a total height to grade cut quality

I can help here.

This is one of those areas where what GIA teaches departs somewhat from lab practice. According to the GIA Diamond Grading Lab Manual's cut-grade reference charts, 63% total depth is a high-cutoff for EX.

When applying GIA methodology diploma-holders are taught to use those charts. That means many GIA trained gemologists and appraisers consider 63% a hard cutoff for the EX grade.





With that said we have all seen diamonds with >63% total height getting EX. For my fellow cut nerds, please note that a 40.4 PA may be considered EX on these charts, but no 40.4 PA qualifies to receive EX in actual grading.

So...some years ago I asked friends at GIA what the deal was. The answer, as @Serg says, is no limiter for total depth enforced when diamonds are graded at the lab. Very broadly put (skipping some minutia) the limiters involve T% PA CA combos. Some of those combos allowed in EX can stretch across 63%, depending on girdle thickness. And until the girdle crosses 4.5% they remain EX.

 

[Rockdiamond]

For the sake of discussion, let's take a hypothetical situation where we compare a 6.45, and a 6.30mm G/VS2 diamonds, both EX cut grade. In this hypothetical situation, the stones have identical light performance. If someone paid less for the smaller spreading diamond, was damage done to the buyer?
To me, this goes to the heart of the issue of cheating in many ways.

It seems that GIA is between a rock and a hard place. Some people won't agree no matter which direction they take.

 

[Serg]

I think we may be saying the same thing, but in a different way. Below is a hand sketch of what I am thinking.

Assuming all other elements remain the same except the girdle thickness, then the pavilion angle would have to change, right? I tried to illustrate this with the red vs blue sketch.

The black sketch shows the extra facet (almost acting like a "star facet" in the side view, except on the pavilion). By adding that facet, you can keep the same pavilion angle of the thicker girdle diamond (blue) but get the advantage of a thinner girdle diamond (red).

@sledge
No, Our statements are very different. In your drawings the right diamond finally has a same girdle thickness and pavilion angle as the original "red" diamond.

 

[Serg]

I can help here.

This is one of those areas where what GIA teaches departs somewhat from lab practice. According to the GIA Diamond Grading Lab Manual's cut-grade reference charts, 63% total depth is a high-cutoff for EX.

When applying GIA methodology diploma-holders are taught to use those charts. That means many GIA trained gemologists and appraisers consider 63% a hard cutoff for the EX grade.





With that said we have all seen diamonds with >63% total height getting EX. For my fellow cut nerds, please note that a 40.4 PA may be considered EX on these charts, but no 40.4 PA qualifies to receive EX in actual grading.
.

How old are such GIA Diamond Grading Lab Manual's cut-grade reference charts? Had been they developed and printed before 2006? I believe they have not any connection with current GIA grading system .

 

[diagem]

diagem said:
I also dont think a slight spread issue should downgrade LP potential (although in some instances it might).

On the other hand I do believe extra facets should depreciate the craftsmanship top grade

I think the key word is slight spread. As I think you are eluding to, if you change too much then your proportions have to change and LP could then be affected, right?

I also agree about depreciating the top grade, and would add that it would be nice to see a note about it being a modified cut with extra facets.

Actually I added "slight spread" because usually conversations discuss RB's as its a RB kind of world, so in such a simple scenario (symmetrical eight fold design) slight spread due to slight girdle thickness might not alter LP too much.

But since my world is more about fancy cuts, thats where girdle thickness can very easily downgrade LP score and be less affected by spread.

Regarding craftsmanship..., if the excellent grade allow minor extra facets then there should be a higher grade echelon for non-cheating craftsmanship.

 

[John P]

How old are such GIA Diamond Grading Lab Manual's cut-grade reference charts? Had been they developed and printed before 2006? I believe they have not any connection with current GIA grading system .

Come on @Serg , you know me better than that. I'm an education junkie. I attended the lab courses soon after they updated to their manual and curriculum in 2006. My copy was printed in 2007 and is connected with the current system.

 

[John P]

For the sake of discussion, let's take a hypothetical situation where we compare a 6.45, and a 6.30mm G/VS2 diamonds, both EX cut grade. In this hypothetical situation, the stones have identical light performance. If someone paid less for the smaller spreading diamond, was damage done to the buyer? To me, this goes to the heart of the issue of cheating in many ways. It seems that GIA is between a rock and a hard place. Some people won't agree no matter which direction they take.

Right. They are not pre-penalizing a diamond for potential harm to a buyer. It makes sense from a clinical grading standpoint.

The wrinkle is the presumption that buyers will know two "1-carat" diamonds can face-up with different spreads. As anyone who sees client-traffic knows, most new buyers have no idea about that. But that's not GIA's fault...

Or is it? [ Cue dramatic music ]

 

[Garry H (Cut Nut)]

Sergey Facetware always dings proportion combinations with depths over 63%.
There is an explanation here: https://www.gia.edu/facetware-help#fd-totaldepth
This table shows clearly the limits for depth for each grade:


But it seems via the explanations on that page that they allow their strange system to arrive at different outcomes to the measured precise outcome. I can not understand how or why that can be permissible, especially when it encourages cutters to push the amount of cheating of consumers.

Is this not unconscionable conduct by any legal or normal consumer perspective?

You have a published rule, but you establish and teach a way to get around the rules???

 

[John P]

Hey Garry, did you completely ignore my posts?

To quote Blazing Saddles: “Harumph!”

 

[Garry H (Cut Nut)]

Hey Garry, did you completely ignore my posts?

To quote Blazing Saddles: “Harumph!”

Yes John, but Sergey demands some direct GIA info (we all know that many times GIA education department and Lab have big conflicts).
So I found it.
I am sure there was more than that in various G&G publications too regarding 63%.
Hard to believe they condone cheating?!?

 

[Serg]

@Garry H (Cut Nut)
Thanks for the link. In fact GIA does not use a total height limitations for EX grade
Cutters used extra facet to reduce girdle thickness and such cheating had not any connection with a total height limitation.

 

[John P]

Dear @Garry H (Cut Nut) and @Serg .

With respect, I told you I can help (and I tried above) but only if you listen. You're both correct. But you're also so anxious to make yourselves understood that you might not be seeking to understand the totality.

Garry... Serg is correct about what GIA does. They don't limit total-depth for the EX grade at their lab locations. Full stop.

Sergey... Garry is correct about what GIA says. They publish 63% as a total-depth limit for EX in their grading manual, and elsewhere, and GIA graduates widely enforce it away from the lab. Full stop.

Perhaps you can agree to agree?

 

[Serg]

Dear @Garry H (Cut Nut) and @Serg .

With respect, I told you I can help (and I tried above) but only if you listen. You're both correct. But you're also so anxious to make yourselves understood that you might not be seeking to understand the totality.

Garry... Serg is correct about what GIA does. They don't limit total-depth for the EX grade at their lab locations. Full stop.

Sergey... Garry is correct about what GIA says. They publish 63% as a total-depth limit for EX in their grading manual, and elsewhere, and GIA graduates widely enforce it away from the lab. Full stop.

Perhaps you can agree to agree?

John,
I believe you did not understand the my post. I wrote "Garry, thanks for the link"

Garry published that I asked, and I said to Garry "Thanks".
what is a reason for the your above post?

 

[John P]

John, I believe you do not understand the my post. I wrote "Garry, thanks for the link" Garry published that I asked, and I said to Garry "Thanks". what is a reason for the your above post?

Two reasons -

1. I provided you with the same depth limit information on Friday - directly from GIA's lab manual. It went unacknowledged.

2. Your post to Garry this morning said (again) << In fact GIA does not use a total height limitations for EX grade >> ... I did not realize you saying << thanks for the link >> meant you also recognize the contradiction between what GIA does and says.

Now I do. Thank you for the clarification.

 

[TODiamonds]

Garry... Serg is correct about what GIA does. They don't limit total-depth for the EX grade at their lab locations. Full stop.

Isn't this the only one that really matters?

 

[John P]

Isn't this the only one that really matters?

Bottom line, yes.

The fallout in my travels (even in this thread) is the number of jewelers who are totally convinced no RB can be EX if it’s over 63% deep. I‘d like to have all the hours back I’ve spent GIA-splaining the contradiction to other pros in my workshops.

 

[OoohShiny]

I can help here.

This is one of those areas where what GIA teaches departs somewhat from lab practice. According to the GIA Diamond Grading Lab Manual's cut-grade reference charts, 63% total depth is a high-cutoff for EX.

When applying GIA methodology diploma-holders are taught to use those charts. That means many GIA trained gemologists and appraisers consider 63% a hard cutoff for the EX grade.





With that said we have all seen diamonds with >63% total height getting EX. For my fellow cut nerds, please note that a 40.4 PA may be considered EX on these charts, but no 40.4 PA qualifies to receive EX in actual grading.

So...some years ago I asked friends at GIA what the deal was. The answer, as @Serg says, is no limiter for total depth enforced when diamonds are graded at the lab. Very broadly put (skipping some minutia) the limiters involve T% PA CA combos. Some of those combos allowed in EX can stretch across 63%, depending on girdle thickness. And until the girdle crosses 4.5% they remain EX.

Bottom line, yes.

The fallout in my travels (even in this thread) is the number of jewelers who are totally convinced no RB can be EX if it’s over 63% deep. I‘d like to have all the hours back I’ve spent GIA-splaining the contradiction to other pros in my workshops.

I am sort of confused.... (not that hard to do, lol).


So GIA sets out grading criteria (within its written literature and training materials) based on hard-limit boundaries for each individual assessment criterion?

Which GIA GGs then use out in the real world when appraising individual stones that come across their bench / desk?


But GIA grading labs apply some mysterious assessment technique based on a mix of the individual criterion?

Which means the hard-limit grading boundaries for each individual criterion are thrown out of the window??




On what basis are the combinations of the individual criterion decided?

Is it a light-performance-based approach, similar to AGS?

Is it a 'beauty'-based approach? (informed by historic views / decisions on 'beauty'?)

Or is it something completely different?


Is it any wonder the general public think the diamond industry is suspiciously opaque when things like this are taking place??!

 

[Karl_K]

The claimed base of the GIA system is they gathered some diamonds, some people, mostly trade members, a few consumers and had them look at diamonds and pick which they liked better.

 

[Karl_K]

Some answers below, some in the post above.

I am sort of confused.... (not that hard to do, lol).


So GIA sets out grading criteria (within its written literature and training materials) based on hard-limit boundaries for each individual assessment criterion?

yes

Which GIA GGs then use out in the real world when appraising individual stones that come across their bench / desk?

yes

But GIA grading labs apply some mysterious assessment technique based on a mix of the individual criterion?

Different from what they teach anyway.

Which means the hard-limit grading boundaries for each individual criterion are thrown out of the window??


Some anyway

Basically what they do in the lab is not what they teach nor what they advertise.

 

[gm89uk]

For the sake of discussion, let's take a hypothetical situation where we compare a 6.45, and a 6.30mm G/VS2 diamonds, both EX cut grade. In this hypothetical situation, the stones have identical light performance. If someone paid less for the smaller spreading diamond, was damage done to the buyer?
To me, this goes to the heart of the issue of cheating in many ways.

It seems that GIA is between a rock and a hard place. Some people won't agree no matter which direction they take.

I think no damage was done to the buyer.

On the flip side of the argument, I'm sure there is rough that makes for a beautiful well performing ~63% diamonds. Should cutters aim for for <62 percent depth and lose valuable carat to avoid being called cheaters? Unless of course they are purposely brillianteering/adding facets to the diamond to cheat

 

[Garry H (Cut Nut)]

Here is the description of the establishment of GIA's cut grading system (minus any references to HCA and their IP borrowing from HCA).

https://www.gia.edu/doc/FA04.pdf

 

[John P]

I am sort of confused.

Right. You're in good company. Can we tap the brakes for a minute?

Here's how I have GIA-splained the existence of the published 63% limiter in the past.

The 63% cutoff used in the manual, Facetware, etc. can be compared to our federal law that requires all school buses to stop at railroad tracks. Even if there's no danger, those drivers are required to stop when they come to the tracks, out of an abundance of caution.

Meanwhile, what GIA is doing at the lab is more complex. So they don't have to stop at the tracks if the situation warrants it.

I realize it's not a perfect explanation. And if someone has a better explanation or simile I am absolutely interested in hearing it.

 

[Karl_K]

@John Pollard
Why not just say....
GIA lies.