GIA Diamond Cut Grading: Problems with Diamond Dock

[Rhino]

Date: 3/17/2006 3:37:34 AM
Author: Serg

BTW,

Rhino, On your nice photo even nice diamond is semi( or quarter ) dead. Even nice diamond can not work completely in DD GIA.

It is bad sign.

Considering that illumination is never perfectly symmetrical or even, I''d have to look into this more. I have a series of photographs I''m putting together of 2 comparison stones so that you can see how they photograph in various lighting environments which depict brightness. Give me a bit and I''ll get it togehter. I wouldn''t arrive at a rash judgement however.

Peace,
Jon

 

[Rhino]

Date: 3/17/2006 3:39:33 PM
Author: belle

Date: 3/17/2006 2:33:38 PM
Author: dhog
Rhino

this is again from a consumers point of view

the photo you posted above looks to me to
have 2 different light sources from the angles
that I can see.

I submit this for all P/S members to look close
in the middle of the photo and then slowly look
up to the top.

is this what I think it is or is it my eye's playing
tricks on me again.

thanks for pointing that out dhog.
what harm is there in a little cut and paste? matching up two different photos and declaring it one...what's the big deal?
surely there is a reason for going through the trouble of trying to perfectly match up two different photos and calling them one original other than differences in lighting.

LOL. In fact I did transverse the picture because in our tutorial on the subject I had the stones in left/right order except for that one and I wanted the graphics on that tutorial to be consistent in left/right viewing.

 

[adamasgem]

Date: 3/16/2006 4:50:02 PM
Author: JohnQuixote


Unless upstream manufacture shifts significantly to steep/deep (ergo steeper/deeper) I still feel consumers are better served by a GIA with a cut grading system over a GIA without one. Yes, there are issues to be worked out, but the overall awareness generated by a lab of their stature implementing this change is very positive (there''s that forest).

I disagree with the highlighted phrase. At least in the past, people knew there wasn''t sufficient information on the paper.
Now they think there is. Which is worse, no information, or WRONG or potentially misleading information, I ask.

 

[JohnQuixote]

Date: 3/17/2006 7:14:10 PM
Author: adamasgem

Date: 3/16/2006 4:50:02 PM
Author: JohnQuixote


Unless upstream manufacture shifts significantly to steep/deep (ergo steeper/deeper) I still feel consumers are better served by a GIA with a cut grading system over a GIA without one. Yes, there are issues to be worked out, but the overall awareness generated by a lab of their stature implementing this change is very positive (there's that forest).

I disagree with the highlighted phrase. At least in the past, people knew there wasn't sufficient information on the paper. Now they think there is. Which is worse, no information, or WRONG or potentially misleading information, I ask.

Well I disagree with the blue highlighted phrase.

When I am wearing my 'corporate (read that as trade) coat' I actually agree with you Marty - for the reasons you state.

But from the standpoint of regular Joe Average, shopping for diamonds for the very first time, I maintain what I said above. 'Normal' people looking at an EGL, IGI or old GIA report with no proportions beyond table and depth don't realize something is missing, and most jewelers certainly won't tell them they need to know more.

Joe: 'Okay. 1 ct, Color D, Clarity VS1... Cool. You've explained everything. Anything else I need to know?'
Jeweler: 'Buy it at your own risk - we have no idea what the crown and pavilion angles are.'

I don't think so.

The internet and jewelers who fully educate clients have reached some people, but the public-at-large knows Carat, Color, Clarity and 'shape' (cut). People have had very little awareness that proportions existed beyond table and depth, and far less awareness about grading systems for cut.

I'm instructing a lecture series where I've sampled hundreds of pedestrian observations from neutral audiences in classrooms. In the mainstream, away from vehicles like Pricescope - or appraisers, or jewelers where good education is part of the buying process, etc - there is not any awareness about shortcomings of previously standard documents like EGL, IGI and old GIA. So... People do not know there isn't sufficient information.

GIA has massive impact. With the new documents will come the spread of AWARENESS that such a thing as a 'grade' for cut actually exists... Even if we have criticisms about the system, it's no longer invisible (applause).

I presented a bit of this before, on this page, and discussion ensued. It's different when seen through trade eyes (where we think about proportions and brillianteering at breakfast), but education is my speciality and I'm firm on this point. Of course, I respect your right to disagree based on your experiences.

 

[michaelgem]

FLASH......

GIA and AGS AGREE THAT PAINTING IS BAD. DA VINCI TURNS OVER IN GRAVE. NEWS AT 11

This following information from inquiries of both AGS and GIA support my belief that the two organizations are fundamentally close on the two major issues of recent discussions, the issue of slightly steep/deep and the issue of painting and digging.

It was an eye opener to me to find how close both their views are on these two subjects. Seeing the trashing GIA has taken on this forum and the obvious bias toward AGS, many reading this forum would be justified in believing that there is a wide chasm between their respective cut grading systems.

The facts appear otherwise.

I was told that the slightly steep/deep example of Jonathan’s would get an AGS1 rather than the 3 or 4 I heard speculated.

The point was made to me that the top grade in a 5-grade system such as GIA’s would better be compared to the top two grades in a 10-grade system, such as AGS’s. The agreement between them is even better on that basis.

Another point of agreement is both GIA and AGS downgrade painting and digging. I was surprised, and I suspect you may be also, to find that very little in the way of painting is allowed in the AGS grading system before the diamond is dropped from AGS0 Ideal. I am told that an index deviation of more than 4° from the upper half index of 11.25° toward the 0° main index will drop a painted diamond from AGS0 Ideal. Only this minor amount of painting (index deviation of the halves toward the mains) is allowed.

GIA and AGS appear to be fundamentally in agreement that slightly steep/deep diamonds are on balance excellent performers. They are in fundamental agreement that painted crown diamond’s are below par performers. Additionally, both systems penalize a diamond for having insufficient spread.

This supports the belief that the difference in cut grading between the two organizations is not in fundamentals, but only in degree. AGS sets the bars on these cut features slightly higher than GIA.

Whether the consumer will discern the difference in beauty between an AGS “triple zero” and the GIA “triple excellent” is an interesting question for speculation. Because they may be identical or only slightly different in performance, only the diamond connoisseurs such as the growing niche market here on the Internet may prefer one over the other.

(The diamonds our Internet connoisseurs will likely prefer will have high optical symmetry, which both organizations toss in with non-optically symmetrical diamonds. High optical symmetry is viewed as simply a matter of taste by both GIA and AGS.)

Michael Cowing

www.acagemlab.com

 

[Garry H (Cut Nut)]

Date: 3/17/2006 6:56:59 PM
Author: Rhino

Date: 3/17/2006 3:39:33 PM
Author: belle

Date: 3/17/2006 2:33:38 PM
Author: dhog
Rhino

this is again from a consumers point of view

the photo you posted above looks to me to
have 2 different light sources from the angles
that I can see.

I submit this for all P/S members to look close
in the middle of the photo and then slowly look
up to the top.

is this what I think it is or is it my eye''s playing
tricks on me again.

thanks for pointing that out dhog.
what harm is there in a little cut and paste? matching up two different photos and declaring it one...what''s the big deal?
surely there is a reason for going through the trouble of trying to perfectly match up two different photos and calling them one original other than differences in lighting.

LOL. In fact I did transverse the picture because in our tutorial on the subject I had the stones in left/right order except for that one and I wanted the graphics on that tutorial to be consistent in left/right viewing.

Jonathon speaks the truth
I pasted the sides back to the other sides - and they are just switched around

 

[Garry H (Cut Nut)]

Love the humour Michael, but not the content

Date: 3/18/2006 12:08:28 AM
Author: michaelgem

FLASH......

GIA and AGS AGREE THAT PAINTING IS BAD. DA VINCI TURNS OVER IN GRAVE. NEWS AT 11

This following information from inquiries of both AGS and GIA support my belief that the two organizations are fundamentally close on the two major issues of recent discussions, the issue of slightly steep/deep and the issue of painting and digging.

It was an eye opener to me to find how close both their views are on these two subjects. Seeing the trashing GIA has taken on this forum and the obvious bias toward AGS, many reading this forum would be justified in believing that there is a wide chasm between their respective cut grading systems.

The facts appear otherwise.

I was told that the slightly steep/deep example of Jonathan’s would get an AGS1 rather than the 3 or 4 I heard speculated.

Have you read the Journal article I posted - that stone is an AGS 2 for light pperformance, and is 35C 41.4Pavilion - so it is very likely that a GIA 36C 41.6P Excellent would be given AGS 3 or 4.

The point was made to me that the top grade in a 5-grade system such as GIA’s would better be compared to the top two grades in a 10-grade system, such as AGS’s. The agreement between them is even better on that basis.

Another point of agreement is both GIA and AGS downgrade painting and digging. I was surprised, and I suspect you may be also, to find that very little in the way of painting is allowed in the AGS grading system before the diamond is dropped from AGS0 Ideal. I am told that an index deviation of more than 4° from the upper half index of 11.25° toward the 0° main index will drop a painted diamond from AGS0 Ideal. Only this minor amount of painting (index deviation of the halves toward the mains) is allowed.

The information I have heardad and been given by PY is that cutters can do what ever they like as long as the ASSET light performance and the girdle thickness / spread / tilt etc rules are not broken. Now it is likely that a severly painted slightly shallow stone would be knocked down for contrast - so it might not be advisable to cut more than 4 degrees or +1 click painting. But that is different to no no no!!

GIA and AGS appear to be fundamentally in agreement that slightly steep/deep diamonds are on balance excellent performers. They are in fundamental agreement that painted crown diamond’s are below par performers. Additionally, both systems penalize a diamond for having insufficient spread.

AGS spread penalty kicks in at 5% and GIA''s is I believe at 8 or maybe 9% - would you like to find a real example of a border line steep deep with a new AGS report to back up those assertions Michael?

This supports the belief that the difference in cut grading between the two organizations is not in fundamentals, but only in degree. AGS sets the bars on these cut features slightly higher than GIA.

Whether the consumer will discern the difference in beauty between an AGS “triple zero” and the GIA “triple excellent” is an interesting question for speculation. Because they may be identical or only slightly different in performance, only the diamond connoisseurs such as the growing niche market here on the Internet may prefer one over the other.

Many manufacturers are dreading the idea that retailers and consumers start asking for tripple excellent GIA - not every piece of rough lets you do that. And as so many people have said - Good and Excellent appearance differences are oftn impossible to detect - I think Peter would be happy to accept a slightly lower sym and polish and still grade as Ideal AGS0 if he could.

(The diamonds our Internet connoisseurs will likely prefer will have high optical symmetry, which both organizations toss in with non-optically symmetrical diamonds. High optical symmetry is viewed as simply a matter of taste by both GIA and AGS.) here we agree - especially since I have seen GIA good sym in H&A''s diamonds

Michael Cowing

www.acagemlab.com

 

[adamasgem]

Date: 3/18/2006 12:08:28 AM
Author: michaelgem

FLASH...... Somewhat doesn''t do their homework

GIA and AGS AGREE THAT PAINTING IS BAD. DA VINCI TURNS OVER IN GRAVE. NEWS AT 11

The facts appear otherwise. Michael. Facts are for those who do their own homework

I was told that the slightly steep/deep example of Jonathan’s would get an AGS1 rather than the 3 or 4 I heard speculated.

If I were you, I would watch myself relying on your "source". If you had taken the trouble to check, you would find that the gem file that Johnathon posted as being from the steep/deep with a supposedly 35.08/41.15 crown/pavilion, really has crown angles, according to the export of the asc file, ranging from approx 34.2 to 34.35 and pavilion angles 40.72 to 40.86, unless I completely misread the ascii text file created from the gem file. Convenient misleading mistake?
(Or was some version of GIA rounding used?

)

Sergey, could you look at the gem file that was posted on the other thread and tell me if I''m wrong please. I''d be happy to appologise if my cynacism was misplaced.




The point was made to me that the top grade in a 5-grade system such as GIA’s would better be compared to the top two grades in a 10-grade system, such as AGS’s. The agreement between them is even better on that basis.

Well why don''t you do the work YOURSELF and prove your point. Overlay the AGS 0 and 1 grade ranges with GIA EX.

I look at it as one is 5 times as likely to get a GIA EX as to get a AGS 0 grade. All depends on how you want to "spin" it.

 

[Serg]

re:I am told that an index deviation of more than 4° from the upper half index of 11.25° toward the 0° main index will drop a painted diamond from AGS0 Ideal. Only this minor amount of painting (index deviation of the halves toward the mains) is allowed.

Michael,
4 degree is not MINOR AMOUNT for painting.
3.75 is 1 click. 1 Click is close for optimum.
2 click is usually bad painting
3 click is not possible technically.

GIA penalty 1 click same for painting and dig out for all diamonds . AGS is not penalty good diamonds with 1 click painted or less.

I sure it is big and important difference.
Do you remember your words How *8 diamonds is beautiful?
Is different between GIA grade "Very good"( or may be even "GOOD") from GIA "Excellent" MINOR AMOUNT? If it is minor amount, I agree with your post.

 

[Serg]

re:Sergey, could you look at the gem file that was posted on the other thread and tell me if I''m wrong please. I''d be happy to appologise if my cynacism was misplaced.


Marty,

Firstly Rhino published images from Helium reports for one pair diamonds.( One diamonds was painted)
Then Rhino published Helium 3D model and photos for other pair diamonds.( One diamonds was painted)
Now Rhino use photos from third pair diamonds( one diamonds is dig out)

Rhino if I miss something, please correct me.

 

[michaelgem]

Re: FLASH......GIA and AGS AGREE THAT PAINTING IS BAD. DA VINCI TURNS OVER IN GRAVE. NEWS AT 11

Sorry to disturb the flow with this attempt to lighten things up and remind folks of the big picture.

The major players here are in solidarity in trashing GIA and have no interest in acknowledging fundamental commonalities among the top grades of both GIA and AGS. These commonalities dwarf the differences in these two cut grading systems.

The heart of what constitutes the best and most beautiful round brilliant lies in some, but not all, of those fundamental commonalities.

I am pointing out only a few of those commonalities, because they are the ones being discussed, and they illustrate how fundamentally alike these two cut grading systems really are.

That is not to imply, as everyone seems to have, that I am in agreement with all the commonalities. I have problems with some of them. The issue of optical symmetry is one.

In summary:

1. GIA and AGS are fundamentally in agreement that slightly steep/deep diamonds are on balance excellent performers. Too steep a crown or too deep a pavilion is heavily downgraded by both.

2. They are in fundamental agreement that painted crown diamond’s, like those with which we are all familiar, are below par performers.

3. Both systems penalize a diamond for having insufficient spread. The difference is in degree.

4. Both organizations toss diamonds with high optical symmetry in with non-optically symmetrical diamonds. High optical symmetry is viewed as a matter of taste by both GIA and AGS.

The difference in cut grading between the two organizations is not in fundamentals, but in degree.

AGS sets the bars on these cut features slightly higher than GIA. By slightly, I mean that it is not clear whether the greater part of the consuming public will discern the difference in beauty between an AGS “triple zero” and the GIA “triple excellent”.

Because top grade diamonds in both systems may be identical or only slightly different in performance, only the diamond connoisseurs, such as the growing niche market here on the Internet, may prefer one over the other.
You can spin this all you want, these facts remain.

Michael Cowing

www.acagemlab.com

 

[Serg]

re:The difference in cut grading between the two organizations is not in fundamentals, but in degree.

Michael, please give your example of difference Which can be Fundamental for cut grade?

BTW What is difference between GIA and IGI cut grades?( If difference between AGS and GIA cut grading in degree just.)

re:The major players here are in solidarity in trashing GIA and have no interest in acknowledging fundamental commonalities among the top grades of both GIA and AGS. These commonalities dwarf the differences in these two cut grading systems.

Michael, I think your statement is not good. ( may be very very bad for research , If You can proof your point , please do not try tell we are bad company)

My goal to show most critical errores( GIA or AGS does not matter for me.)

AGS have done wrong step in right direction, GIA have done right step in wrong direction.
For my test wrong step in right direction is much better, then right step in wrong direction.

 

[RockDoc]

Michaelgem wrote:


2. They are in fundamental agreement that painted crown diamond’s, like those with which we are all familiar, are below par performers.


BELOW PAR PEFORMERS??????????

Considering that PAR looking at wide amount of cut quality variances offered to consumers, this seems to infer that diamond with painted crowns perform less than what would be the average cut grade sold across the retail market?

That statement to me, is patently false and is like saying a pup tent is the same as a house and is professionally reckless and misleading.

Rockdoc

 

[michaelgem]

Sergey,

I want to acknowledge my enormous respect for you and Yuri and the individual scientists at Octonus.

You are the major player here from a scientific standpoint; not only because of your and your organization’s math-science credentials and research efforts, but also because of the tools you have graciously provided us all such as DiamCalc and now Helium.

We have all benefited and continue to benefit enormously from Octonus’s and especially your individual efforts. It is an intellectual debt that I can only attempt to repay by my research efforts, which employ the tools you have provided this industry.

I have been quick to point out that you criticize AGS as well as GIA when you see problems in either system.

Recall for example my acknowledgement that:

“Sergey is absolutely correct when he points out that: " Pav 41.2 Cr 35 is a really nice stone. It does not have the death ring in stereovision. This diamond is pointing to an AGS cut grade mistake (I mentioned this on PS several months ago)"

I thought that, by their actions, it should be obvious who those are that trash GIA to their own ends. These individuals exaggerate and spin differences all out of proportion to further their own agenda. My effort here is to restore the correct sense of proportion to these differences.

The commonalities between the cut grading systems of GIA and AGS, whether you agree with each of them or not, dwarf the differences in these two cut grading systems.

I believe that the heart of what constitutes the best and most beautiful round brilliant lies in some, but not all, of those fundamental commonalities, and not in the differences.

Michael Cowing

www.acagemlab.com

 

[michaelgem]

Re: 2. They are in fundamental agreement that painted crown diamond’s, like those with which we are all familiar, are below par performers.

BELOW PAR PEFORMERS??????????

Considering that PAR looking at wide amount of cut quality variances offered to consumers, this seems to infer that diamond with painted crowns perform less than what would be the average cut grade sold across the retail market? Rockdoc

LMAO.

That is not at all how I meant you to take that statement, Rock.

Both organizations see enough negative effects from painting to the degree with which we are all familiar to remove those diamond’s from their respective top grades.

Please do not infer that I agree, only that I know it to be a fact.

Par is a term derived from golf. Par for me is such a lofty goal that I see it as unattainable. They call me the double-bogy man.

Let me reword this statement to correct any possible misinterpretation.

2. GIA and AGS are in fundamental agreement that painted crown diamond’s, like those with which we are all familiar, have negative optical performance issues excluding them from each organization’s respective top grade.

Geez Louise, you have to take a course in lawyerese to avoid being spun on this forum.

Michael Cowing

www.acagemlab.com

 

[adamasgem]

Date: 3/18/2006 9:58:48 AM
Author: michaelgem

In summary:

1. GIA and AGS are fundamentally in agreement that slightly steep/deep diamonds are on balance excellent performers. Too steep a crown or too deep a pavilion is heavily downgraded by both.
I guess it all depends on what the definitions of "slightly" and "too" are..

2. They are in fundamental agreement that painted crown diamond’s, like those with which we are all familiar, are below par performers. I don''t know where you are getting "your" information from here, or you might be confused, but if you equate an AGS "ideal" to a "below par performer", then you must be thinking of golf. I''d love to shoot "below par" like Tiger Woods. Of course, GIA seems to have a different "definition" for almost anything. I guess they might consider Tiger Woods a "hacker".

3. Both systems penalize a diamond for having insufficient spread. The difference is in degree. I agree, the difference is in the definition of "degree"

4. Both organizations toss diamonds with high optical symmetry in with non-optically symmetrical diamonds. High optical symmetry is viewed as a matter of taste by both GIA and AGS. Here again I disagree, going backwards and basing a cut crade on "rounded" averages and thus assuming a physically (and therefore optically symmetric) diamond versus using the actual scan of the stone with its symmetry faults are two FUNDAMENTALLY different things!!!!!!!!

The difference in cut grading between the two organizations is not in fundamentals, but in degree. To me, a BIG degree

AGS sets the bars on these cut features slightly higher than GIA."Slightly?" By slightly, I mean that it is not clear whether the greater part of the consuming public will discern the difference in beauty between an AGS “triple zero” and the GIA “triple excellent”. Here I might tend to agree with you, given the that the vast majority of diamonds sold by mass merchandisers are relative junk, and people still buy them.

Because top grade diamonds in both systems may be identical or only slightly different in performance, only the diamond connoisseurs, such as the growing niche market here on the Internet, may prefer one over the other. Well, there is some overlap between the two cut grade system results, as to be expected, but there appears to be a BIG difference in the size of the 10 ring, sort of like the difference between the 10 ring in olympic free pistol and the 10 ring in combat pistol shooting

You can spin this all you want, these facts remain. I guess we have a fundamental difference in what we consider "facts".

 

[michaelgem]

Sergey and Garry,

Re: MINOR AMOUNT? If it is minor amount, I agree with your post. Sergey.

Whether or not we feel that 4 degrees is a major or minor amount for painting is debatable but unimportant.

The amount of painting with which we are all familiar, is considered major enough to drop these diamonds from the top grades in both GIA’s and AGS’s grading systems. This is a fact obtained from and told to me by both organizations.

That is one of the commonalities, that I am pointing out.

BTW, for those reading who may not be aware, one click is 3.75 degrees only in a 96-index wheel, which is typically used on a faceting machine to cut colored stones, not diamonds. The typical “tang” used in diamond cutting only has clicks at the normal mains and halves indexes. The halves indexes are 11.25 degrees away from the main indexes.

To cut the painted crown halves, the diamondtaire sets the index to the nearest main click and then “cheats” or adjusts a small amount to either side of each main.

You cannot obtain the optical properties that are used to sell these particular diamonds with a four degree or less amount of painting.

Michael Cowing

 

[strmrdr]

michaelgem
This is a graded ags0 diamond with painted girdles.
That does not jive with what your saying.
GIA graded a similar diamond as vg or g because of the painting.


http://www.whiteflash.com/hearts_arrows/A-Cut-Above-H-A-cut-diamond-2167547.htm#

 

[strmrdr]

Resized cert to fit in this post without wrecking the format of the thread.
The full sized image is at the above link

 

[JohnQuixote]

Date: 3/18/2006 12:46:50 PM
Author: michaelgem




Let me reword this statement to correct any possible misinterpretation.

2. GIA and AGS are in fundamental agreement that painted crown diamond’s, like those with which we are all familiar, have negative optical performance issues excluding them from each organization’s respective top grade.

Geez Louise, you have to take a course in lawyerese to avoid being spun on this forum.

Michael Cowing

www.acagemlab.com

Michael, thank you for your attempts to find common ground.

Your statement is correct, but the phrase 'like those with which we are all familiar' is where we diverge.

On this forum we are all familiar with diamonds having premium supersymmetry where crown painting may be used in finishing. In these cases, when the girdle is consistent and not wavy, and the result is additive, the diamond should not be downgraded. AGS awards such diamonds the highest grade. GIA does not.

As per Serg' numbers, GIA has decided to downgrade a certain level of digging or painting, ‘by the numbers’ alone. This protects against situations where the intent was to retain weight at the expense of beauty. Average consumers in common situations (like the mall) are protected - and that’s positive. Unfortunately it stereotypes other, carefully crafted, premium diamonds as behaving in a negative way when they do not. Many here feel that a small baby was thrown out with the bath water. Carefully finished premium diamonds are painted on purpose. Coupled with optical symmetry, these diamonds can be among the world's finest. GIA is lumping this tiny percentage of premium makes in with the larger percentage of ‘save the weight’ cases.

Meanwhile, AGS studies the girdle in their proportions evaluation and accounts for its visual impact in their light performance metric. Every diamond is specifically measured for performance, so a diamond where brillianteering is additive acquires the Ideal grade. If the brillianteering (whether traditional, dug or painted) was deleterious it will not.

With careful, premium optical symmetry beauty was the priority, it was not about saving weight. If the girdle is consistent and the painting was deliberately designed to beautify it should not be downgraded. Would you concur?

 

[strmrdr]

Actual image of the diamond.
All images are copyright by Whiteflash used for educational use.

michaelgem
I admire that your here to give some balance to the discussion but what your saying does not fit.

 

[adamasgem]

Date: 3/18/2006 2:07:40 PM
Author: michaelgem

The amount of painting with which we are all familiar, is considered major enough to drop these diamonds from the top grades in both GIA’s and AGS’s grading systems. This is a fact obtained from and told to me by both organizations.

Sir.. I think you better recheck your so called "facts"...

AGS has published a set of examples of painting and digging parameters that would potentially get an AGS 0, and you must know that AGS ray traces to establish their cut grades, which accounts for ALL 57 facets, and their interaction, unlike GIA

Additionally I''m posting a png file that I was sent (and you were copied on) that is an AGS4, but supposedly a GIA EX according to facetware.. Sort of a boundary condition, which sort of disproves your 5 versus 10 grade implication of AGS 0 +1 = GIA EX

" It''s a 41.2 pavilion, 36.5 crown, 57 table, 3.5% girdle at the mains, star length of 55% and lower girdle height of 81.5% which equals 80% lower girdle length"

 

[michaelgem]

Sergey asks: Michael, please give your example of a difference that can be Fundamental for a cut grade?

There are others, but I will offer you two that I discuss in my article “The Eye of the Diamond” at http://www.acagemlab.com/article4/eyeofdia.htm

Both are in agreement with the top grades in GIA’s and AGS’s grading systems.

When a diamond''s pavilion is ideal cut, its pupil, or innermost ring of reflections will be about a third the size of the table. If this section is larger than one half the table, you are not looking at an Ideal cut diamond.
If the middle ring table appears noticeably greater than six-tenths of the diamond''s diameter, you are also not looking at an Ideal cut diamond.

Of these two fundamental aspects of the best diamnd cutting, the size of the inner ring, table reflection is most critical to diamond performance and beauty. This dictates a pavilion angle close to 41 degrees. GIA and AGS have opened the table restriction a slight, but not paticulary noticable, percentage beyond 60.

Michael Cowing

www.acagemlab.com

 

[Garry H (Cut Nut)]

You did not address most of my issues Michael - you simply restated your case.

Date: 3/18/2006 1:10:18 AM
Author: Garry H (Cut Nut)
Love the humour Michael, but not the content

Date: 3/18/2006 12:08:28 AM
Author: michaelgem


FLASH......

GIA and AGS AGREE THAT PAINTING IS BAD. DA VINCI TURNS OVER IN GRAVE. NEWS AT 11

This following information from inquiries of both AGS and GIA support my belief that the two organizations are fundamentally close on the two major issues of recent discussions, the issue of slightly steep/deep and the issue of painting and digging.

It was an eye opener to me to find how close both their views are on these two subjects. Seeing the trashing GIA has taken on this forum and the obvious bias toward AGS, many reading this forum would be justified in believing that there is a wide chasm between their respective cut grading systems.

The facts appear otherwise.

I was told that the slightly steep/deep example of Jonathan’s would get an AGS1 rather than the 3 or 4 I heard speculated.

Have you read the Journal article I posted - that stone is an AGS 2 for light pperformance, and is 35C 41.4Pavilion - so it is very likely that a GIA 36C 41.6P Excellent would be given AGS 3 or 4.

The point was made to me that the top grade in a 5-grade system such as GIA’s would better be compared to the top two grades in a 10-grade system, such as AGS’s. The agreement between them is even better on that basis.

Another point of agreement is both GIA and AGS downgrade painting and digging. I was surprised, and I suspect you may be also, to find that very little in the way of painting is allowed in the AGS grading system before the diamond is dropped from AGS0 Ideal. I am told that an index deviation of more than 4° from the upper half index of 11.25° toward the 0° main index will drop a painted diamond from AGS0 Ideal. Only this minor amount of painting (index deviation of the halves toward the mains) is allowed.

The information I have heardad and been given by PY is that cutters can do what ever they like as long as the ASSET light performance and the girdle thickness / spread / tilt etc rules are not broken. Now it is likely that a severly painted slightly shallow stone would be knocked down for contrast - so it might not be advisable to cut more than 4 degrees or +1 click painting. But that is different to no no no!!

GIA and AGS appear to be fundamentally in agreement that slightly steep/deep diamonds are on balance excellent performers. They are in fundamental agreement that painted crown diamond’s are below par performers. Additionally, both systems penalize a diamond for having insufficient spread.

AGS spread penalty kicks in at 5% and GIA''s is I believe at 8 or maybe 9% - would you like to find a real example of a border line steep deep with a new AGS report to back up those assertions Michael?

This supports the belief that the difference in cut grading between the two organizations is not in fundamentals, but only in degree. AGS sets the bars on these cut features slightly higher than GIA.

Whether the consumer will discern the difference in beauty between an AGS “triple zero” and the GIA “triple excellent” is an interesting question for speculation. Because they may be identical or only slightly different in performance, only the diamond connoisseurs such as the growing niche market here on the Internet may prefer one over the other.

Many manufacturers are dreading the idea that retailers and consumers start asking for tripple excellent GIA - not every piece of rough lets you do that. And as so many people have said - Good and Excellent appearance differences are oftn impossible to detect - I think Peter would be happy to accept a slightly lower sym and polish and still grade as Ideal AGS0 if he could.

(The diamonds our Internet connoisseurs will likely prefer will have high optical symmetry, which both organizations toss in with non-optically symmetrical diamonds. High optical symmetry is viewed as simply a matter of taste by both GIA and AGS.) here we agree - especially since I have seen GIA good sym in H&A''s diamonds

Michael Cowing

www.acagemlab.com

In addition - as Sergye points out - there is a fundemental difference between the approaches used.
GIA will cause a type of commoditization because they can not grade other than round.
AGS have this problem too for new cuts - but at least as a start out system - AGS have a more creative method for traditional other cuts.

 

[michaelgem]

Go ahead, shoot the messenger. Or better yet, spin him to death.

I am simply relaying what I have been told by GIA and AGS.

Re:
I admire that your here to give some balance to the discussion but what your saying does not fit. Strmrdr

What? If it does not fit you must acquit?

I am sympathetic with Strmrdr, Brian and John and their belief in the obvious beauty of their diamonds. Why do both GIA and AGS throw their diamonds in with non-optically symmetric diamonds? Why do both AGS and GIA down grade their painted diamonds in the latest versions of both systems?

Remember I said “the heart of what constitutes the best and most beautiful round brilliant lies in some, BUT NOT ALL, of those fundamental commonalities. “

”I am pointing out only a few of those commonalities, because they are the ones being discussed, and they illustrate how fundamentally alike these two cut grading systems really are. “

Michael Cowing

www.acagemlab.com

 

[adamasgem]

Date: 3/18/2006 12:46:50 PM
Author: michaelgem


Geez Louise, you have to take a course in lawyerese to avoid being spun on this forum.

Michael, you seem to have forgotten a lot about science, in that, like law, the words, or even the punctuation, can convey an entirely different message, intentionally or otherwise. (Forget spelling

) If you can''t stand the heat, get out of the fire..

Science is not about "weasel" wording (like some of the stuff I have read on this and other threads).
Business, marketing, politics and hype are ALL about the use of "weasel wording".

 

[adamasgem]

Date: 3/18/2006 3:46:25 PM
Author: michaelgem

Go ahead, shoot the messenger. Or better yet, spin him to death.

I am sympathetic with Strmrdr, Brian and John and their belief in the obvious beauty of their diamonds. Why do both GIA and AGS throw their diamonds in with non-optically symmetric diamonds? Why do both AGS and GIA down grade their painted diamonds in the latest versions of both systems?

You are sounding more and more like a parrott, repeating the same misstatements of fact, something akin to "I did not have sex with that women".

 

[JohnQuixote]

Date: 3/18/2006 3:46:25 PM
Author: michaelgem


I am sympathetic with Strmrdr, Brian and John and their belief in the obvious beauty of their diamonds. Why do both GIA and AGS throw their diamonds in with non-optically symmetric diamonds? Why do both AGS and GIA down grade their painted diamonds in the latest versions of both systems?

In fact, we believe in the obvious beauty of many configurations. Strm is independent, btw. He is not connected with WF, except as a long-time observer of our products and approaches.

And Michael, the blanket statement about downgrading isn't representative of what's occuring. I asked a question in a post above (posted 2:48:55 PM). Do you concur?

 

[WinkHPD]

I believe that this picture will fit on one screen. It is the same picture as was posted above. It shows the ASET image at 30 and 40 blue and the fire metric. Face up and I believe at 30 degree tilt. As you can see from the fire metric there is little fire in the center of the stone and some nice fire at the outer edges (shown in gold).

Wink

 

[michaelgem]

John and Brian,

You are asking me: With careful, premium optical symmetry beauty was the priority, it was not about saving weight. If the girdle is consistent and the painting was deliberately designed to beautify it should not be downgraded. Would you concur?

That we are in agreement is clear from my saying:

I am sympathetic with Strmrdr, John and Brian and their belief in the obvious beauty of their diamonds. Why do both GIA and AGS throw their diamonds in with non-optically symmetric diamonds? Why do both AGS and GIA down grade their painted diamonds in the latest versions of both systems?

These are questions members of this forum should direct to both organizations, not just GIA.

Michael Cowing

www.acagemlab.com