GIA Diamond Cut Grading: Problems with Diamond Dock

[WinkHPD]

Here is the same stone, in diamcalc shown in office lighting.

Here is the data for the stone. This is from an email received from Peter Yantzer sent to several of us involved in this discussion. Diamcal shows it to be an AGS 5, but if Peter says it is a 4 then it is a pretty safe bet that it is a 4.

Wink

Hi Guys:

Here''s a worst case comparison between AGS and GIA. The stone is a steep / deep. It gets a cut grade of AGS 4 from us - deductions of 2 for face-up brightness, 0.6 for face up leakage, 0.6 for face up contrast, and 1 for weight ratio. GIA gives it an Excellent. 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.

 

[WinkHPD]

Here is the DMC file for those of you with Diamcalc who wish to play with it.

Wink

 

[michaelgem]

This brief interlude to look for common ground was brought to you courtesy of www.acagemlab.com.

Have to return to work.

You may now return to your regularly scheduled program of bashing and trashing.

 

[RockDoc]

Bashing and Trashing......


Don''t think so. A lot of experts and interested consumers are merely correcting mis-statements.

AGS and GIA are on different levels of their cut grading methodologies.

Whether they are as close as you point out, or further apart, as many other express, is not bashing or trashing.

I believe it is the most sincere effort by many to encourage the two systems to be grading on a simlar level.


Something I am curious about, and don''t think it is expressed as an attack, but gotta ask you why is the avatar you selected is an avatar with a wizard using a crystal ball?

Rockdoc

 

[JohnQuixote]

Date: 3/18/2006 4:40:01 PM
Author: 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

Michael,

Brian has been involved in other efforts for several days, so it's my observations here. I don't speak with his expertise and perhaps he might see what you're suggesting as 'in agreement' more clearly than I do (?)

 

[michaelgem]

I want to add further clarification as regards the “major” painting done to obtain the performance characteristics of the painted diamonds with which we are all familiar.

I noted that this amount of painting is 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 recently told to me by both organizations.

That is one of the commonalities between AGS and GIA that I am pointing out.

In discussion with AGSL I was told cutters should restrict their painting within 4° for an AGS0. Supporting this statement was a list sent me of 1500 proportion sets, having various degrees of painting and digging, which has been available to cutters wishing to obtain AGS 0 cut grades. The greatest amount of painting on this list was 3.75°

You cannot obtain the optical properties that are the hallmark of these particular diamonds with a four degree or less painting. Typically, seven or more degrees of painting is needed.

Due to all the uproar these statements occasioned, I called AGSL again to make doubly sure of my facts.

I learned this afternoon that there are no hard and fast, published boundaries to painting that preclude a diamond from getting an AGS 0. On a case by case basis, the proportion set would have to be analyzed for brightness, contrast, and dispersion to see if a given instance of painting makes AGS 0 or not. The four degrees mentioned is a recommendation.

Anyone is invited to submit data files to see if the degree of painting they are doing makes AGS0 or not.

Michael Cowing

www.acagemlab.com

 

[dhog]

Date: 3/18/2006 11:30:39 PM
Author: michaelgem

I want to add further clarification as regards the “major” painting done to obtain the performance characteristics of the painted diamonds with which we are all familiar.

I noted that this amount of painting is 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 recently told to me by both organizations.

That is one of the commonalities between AGS and GIA that I am pointing out.

In discussion with AGSL I was told cutters should restrict their painting within 4° for an AGS0. Supporting this statement was a list sent me of 1500 proportion sets, having various degrees of painting and digging, which has been available to cutters wishing to obtain AGS 0 cut grades. The greatest amount of painting on this list was 3.75°

You cannot obtain the optical properties that are the hallmark of these particular diamonds with a four degree or less painting. Typically, seven or more degrees of painting is needed.

Due to all the uproar these statements occasioned, I called AGSL again to make doubly sure of my facts.

I learned this afternoon that there are no hard and fast, published boundaries to painting that preclude a diamond from getting an AGS 0. On a case by case basis, the proportion set would have to be analyzed for brightness, contrast, and dispersion to see if a given instance of painting makes AGS 0 or not. The four degrees mentioned is a recommendation.

Anyone is invited to submit data files to see if the degree of painting they are doing makes AGS0 or not.


Michael Cowing


www.acagemlab.com

what kind of optical gains could one obtain at these
higher numbers and as you said earlier we more than likely
wouldn''t be able to see it.

At least for now they must be allowing it

 

[dhog]

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

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.

COOL gary said you did the cut and paste deal

 

[Kaleigh]

Date: 3/18/2006 5:16:51 PM
Author: RockDoc
Bashing and Trashing......


Don''t think so. A lot of experts and interested consumers are merely correcting mis-statements.

AGS and GIA are on different levels of their cut grading methodologies.

Whether they are as close as you point out, or further apart, as many other express, is not bashing or trashing.

I believe it is the most sincere effort by many to encourage the two systems to be grading on a simlar level.


Something I am curious about, and don''t think it is expressed as an attack, but gotta ask you why is the avatar you selected is an avatar with a wizard using a crystal ball?

Rockdoc

A voice of reason, how refreshing. Keep it on track. No one is bashing or trashing here.

 

[Garry H (Cut Nut)]

Date: 3/18/2006 11:30:39 PM
Author: michaelgem


I learned this afternoon that there are no hard and fast, published boundaries to painting that preclude a diamond from getting an AGS 0. On a case by case basis, the proportion set would have to be analyzed for brightness, contrast, and dispersion to see if a given instance of painting makes AGS 0 or not. The four degrees mentioned is a recommendation.

Michael Cowing

www.acagemlab.com

Michael, one of your "facts" was wrong (as I pointed out).

Will you please also answer my other questions in your "humorous" post?

This would be more helpful than repeating the same info about how "similar" the two systems are.

On 2 fronts they are not - neither structurally - nor in terms of their results.

You need not be a rocket scientist to know this

e.g. see the thread where John Quiotie shows that the vast majority of GIAA's grades are outside AGS's.

The stone I studied in the journal article is not the most extreme example - it is more extreme than Rhino's though. It has a slightly thickish girdle - a stone can have steeper deeper proportions and a thin girdle and scrape in to gIA's grades with much lower AGS grades.

And then there is the stone that gets AGS 1 light performance and GIA Poor.

Again I would like someone to find a GIA Excellent stone we can scan and send to AGS that is near the GIA steep deep boundary. (Wink / Peter's example has not been graded by gIA - it is a virtual stone - for that reason Wink, it could outperform a real stone with even the tinyest sym variations - so that could explain a differnece between DiamCalc / chart predictions and AGS actual ASSET data).

 

[Garry H (Cut Nut)]

Date: 3/18/2006 4:43:41 PM
Author: Wink
Here is the DMC file for those of you with Diamcalc who wish to play with it.

Wink

Wink I did a little exercise to show that labs should grade the diamond and not try to use ''rules''.

The top DiamCalc is the one you attached - and these numbers are its light return which is pretty bad.

Below I have used the same stone proportions - but I played with the indexing

I painted the upper girdles a lot - 6 degrees.
And I dug out the pavilion by 2 degrees.

I think this would make a huge improvement. (I would still not want to own or sell it though).

Michael this is an example of just how complex it is to grade diamonds with a parametric proportion system (as GIA have attempted to do).
I realised 3 years ago that HCA (which is just what GIA now do, without credit) would never be a grading system - just a sight unseen rejection system.

Labs should work on grading diamonds or 3D models - they should never be grading based on proportions.




(BTW Wink - it is better to put .Gem files up because then non DiamCalc users can open and viwe them)

 

[Garry H (Cut Nut)]

The photo's in the journal article http://journal.pricescope.com/Articles/37/10/GIA-Excellent-Cut-Grade-Case-Study.aspx of the CZ's werre taken rather hurriedly.
(and it is not easy with my little hand held camera)

So I took a few more - this lot are taken during the day in offices and my store. Some of the office ones have light filtered through a window as well as overhead fluoro.

Good stones on the left.
The GIA diamond dock photo of the same stones are on the gray tray.

 

[Garry H (Cut Nut)]

And these were taken at home.
Fluoro, halogens etc
Some were in very low light.

(and BTW these stones both have the same weight. One is 6.5mm and one is 6.25mm. In lower lighting the stone on the right looks quite a lot smaller - especially in lower lighting levels.)

 

[strmrdr]

Garry can we get bigger pictures of the 2 marked here together and what is the lighting conditions in the none DD picture?
They are close at this image size.

 

[strmrdr]

After looking at the DD pictures and some others, I think the DD is looking like its a too dark envirement with all the gray which the diamond is picking up.
Even if the lighting was good the gray is making the diamonds look blah.
Id like to see the DD walls covered in red paper then take the picture.

Does it look that way in person?

 

[dhog]

Date: 3/19/2006 5:59:11 AM
Author: Garry H (Cut Nut)
And these were taken at home.

Fluoro, halogens etc

Some were in very low light.


(and BTW these stones both have the same weight. One is 6.5mm and one is 6.25mm. In lower lighting the stone on the right looks quite a lot smaller - especially in lower lighting levels.)

I think these photos show very well 1 of the problems with diamond dock at least to me.

does the dd have a hole in it under the stones to go along
with the light funneling groove.

although I am a little wet behind the ears as my wife would say



maybe you could use a black jewelry box under the dd lighting
for more contrast and less light absorbtion.

thanks gary for the ex. photos

 

[michaelgem]

This brief interlude to look for common ground was brought to you courtesy of www.acagemlab.com.

Have to return to work.

You may now return to your regularly scheduled program of bashing and trashing.

Bashing and Trashing...... Don''t think so. Rockdoc

No one is bashing or trashing here. Kaleigh

I suppose everyone has their own threshold for what they consider "Bashing and Trashing".

Some, not referring to either Kaleigh or Rockdoc, simply turn a blind eye toward it when it suits them. Perhaps they are in basic agreement with the trasher.

Some (and I certainly except most like Rockdoc and Kaleigh) even get enjoyment out of witnessing and encouraging the disparagement of others.

Perhaps I am too sensitive to trashing and bashing and have too low a threshold.

Casting aspersions on someone''s character, honesty, motivations, or ethics is a form of bashing and trashing that is needless in technical discussions on forums like this.

Statements like this recent example exceed my threshold, but, based on the words of Rockdoc and Kaleigh, apparently not others'':

>>

Speaking from experience, your threshold will be a lot lower when you are the trashee.

Michael Cowing

www.acagemlab.com

 

[Rhino]

Catching up here as time allows.

Firstly ... Garry, thank you for pointing out the truth of my statement.

Hi Marty,

In regards to this comment ...

Date: 3/18/2006 3:18:06 AM
Author: adamasgem

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?

)

As stated in that thread, Sergey had asked me for the Gem file comparisons of the 2 H&A diamonds, one painted one without. NOT the original comparison I posted. Per Sergey''s request I gave him precisely what he asked for.

The original comparison was indeed of a 35.1/41.2. I had posted the proportion data of the original comparisons as the very first graphics in that thread.

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

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.

This is a good point Mike. I would make one correction though. AGS is actually an 11 grade system instead of a 10.

Peace,

 

[Rhino]

Date: 3/18/2006 4:35:41 AM
Author: 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.

Your right on track Sergey. In each picture or file comparison I posted I believe I made it clear which diamonds we were comparing in that post. If any comparison I posted was unclear, my apologies.

 

[adamasgem]

Date: 3/19/2006 11:58:27 AM
Author: michaelgem

Speaking from experience, your threshold will be a lot lower when you are the trashee.

Michael Cowing

www.acagemlab.com

Michael.. Maybe I am not politically correct, but when I, and others, are continually subjected to to "mis-information" then I call a spade, a spade, as the constant parroting of mis-information effects my sensitivities. ESPECIALLY WHEN IT WASTES EVERYONE''S TIME AND ENERGY

You spoke of "motivations", please explain your motivations for statements like:

"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. "

Maybe a little more "exposure" is in order here...

Also, just as newspapers do, perhaps you might title your posts with the word "RETRACTION" , as a few more are in order here..

And as to my supposed "trashing" of Organizations, and their "holy" pronouncements, I can back my commentaries up with documentation of constantly changing and internal widening of so called "standards", to what, in my opinion, is to the detriment of the public at large, and for those of us who have to try to explain to those who ask us, for example, that the stone that GIA calls an EX would get an AGS 4, and that just because two stones get a GIA EX, one may be "worth" considerably more than another, both at the wholesale and retail level(s).


If you can''t stand the heat, get out of the frying pan.. stop your whining

 

[Serg]

I do not like lost time in empty discussion more. We need more hard facts.

I am ready invest 5.000-10.000$ to small MSS

Part 1 GIA Excellent
1) Crown is fix
2) Pavilion step 0.2 degree. 40.6, 41, 41.2, 41.4, 41.6


Part 2
click Painted crown. Same crown Pav 40.6, Pav 40.4( I will try receive just Good here)



Part 3


Some GIA very good ( 3-4 diamonds)
40.4 , 40.8 + some other diamonds



All ideal symmetry. Clarity an color are good for sells. Diameter 5-6 mm

I will send all diamonds to GIA and AGS.

This MSS will available for different appraisers and consumer research at least 3 months.

Welcome to invest Money, Time, Ideas, service. Hope Garry will help.

Our study will open during all steps.

 

[Serg]

I think most interesting crown for such tests is 35 degree( 34 degree is very interesting too)
Table =57%

http://www.diamondcut.gia.edu/charts/57_table.html

 

[michaelgem]

Hi Bill,

Re: Something I am curious about, and don''t think it is expressed as an attack, but gotta ask you why is the avatar you selected an avatar with a wizard using a crystal ball? Rockdoc

Your question prompted me to replace the arbitrarily selected wizard avatar with this new one.

Hope it is not too disturbing. I am not good looking like Garry and Jonathan, nor can I strike an athletic pose like Wink.

Michael

 

[JohnQuixote]

(edited - misread a quote)

Date: 3/19/2006 11:58:27 AM
Author: michaelgem


Perhaps I am too sensitive to trashing and bashing and have too low a threshold.

Thresholds vary, no need to second-guess your own. I do hope discussions continue in a productive manner. Have you read Garry's journal article? If so I am interested in your comments.

 

[adamasgem]

Date: 3/19/2006 12:31:48 PM
Author: Rhino
Catching up here as time allows.

Firstly ... Garry, thank you for pointing out the truth of my statement.

Hi Marty,

In regards to this comment ...

Date: 3/18/2006 3:18:06 AM
Author: adamasgem

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?

)

As stated in that thread, Sergey had asked me for the Gem file comparisons of the 2 H&A diamonds, one painted one without. NOT the original comparison I posted. Per Sergey''s request I gave him precisely what he asked for.

The original comparison was indeed of a 35.1/41.2. I had posted the proportion data of the original comparisons as the very first graphics in that thread.


I, and others, had previously requested that you post the gem or dmc files of the stones you used in your "study", which was what the thread was about, steep/deep versus painted, so if I made a mistake in assuming that that was the post(s) you were referring to, I sincerely APPOLOGISE, if I made the wrong assumption. Again, would you please post the appropriate files requested. I becomes a problem to go back and reread an entire thread if things are not made clear.

 

[RockDoc]

Date: 3/19/2006 2:15:42 PM
Author: michaelgem

Hi Bill,

Re: Something I am curious about, and don''t think it is expressed as an attack, but gotta ask you why is the avatar you selected an avatar with a wizard using a crystal ball? Rockdoc

Your question prompted me to replace the arbitrarily selected wizard avatar with this new one.

Hope it is not too disturbing. I am not good looking like Garry and Jonathan, nor can I strike an athletic pose like Wink.

Michael

MC

This is more academic looking.

One of these days, I''ll change mine...

 

[WinkHPD]

Date: 3/19/2006 2:15:42 PM
Author: michaelgem
Hi Bill,


Re: Something I am curious about, and don''t think it is expressed as an attack, but gotta ask you why is the avatar you selected an avatar with a wizard using a crystal ball? Rockdoc


Your question prompted me to replace the arbitrarily selected wizard avatar with this new one.


Hope it is not too disturbing. I am not good looking like Garry and Jonathan, nor can I strike an athletic pose like Wink.


Michael

LOL! Michael, I have always thought you a handsome man, and your avatar bears this out nicely, I like it.

But strike an athletic pose? Man, that is me surviving, barely, Killer Death Fang Falls. No time for posing! (Okay so it''s called Howard''s Plunge in real life, but ya gotta admitt Killer Death Fang Falls sounds much more dramatic!)

I was just lucky that there was a photographer on the bank that day and she gave me a copy of her photos. In the one just before this my kayak was sticking straight up in the air as I was spit out of a hole, just barely managing to stay upright, it was a VERY exhilarating experience.

Wink

 

[JohnQuixote]

Date: 3/19/2006 2:15:42 PM
Author: michaelgem

Hi Bill,

Re: Something I am curious about, and don''t think it is expressed as an attack, but gotta ask you why is the avatar you selected an avatar with a wizard using a crystal ball? Rockdoc

Your question prompted me to replace the arbitrarily selected wizard avatar with this new one.

Hope it is not too disturbing. I am not good looking like Garry and Jonathan, nor can I strike an athletic pose like Wink.

Michael

All you rugged, smart looking guys are enough to make me want to go work out and read a book.

 

[WinkHPD]

Date: 3/19/2006 1:00:09 PM
Author: Serg


I do not like lost time in empty discussion more. We need more hard facts.

I am ready invest 5.000-10.000$ to small MSS

Sergy, that sounds awesome. May I ask only what is MSS? Having a stone cut and submitted to both labs and subject to open viewing and examination by all parties sounds very useful in furthering the amount of difference between the two major educational gem labs in this country.

Wink

 

[adamasgem]

Date: 3/19/2006 2:15:42 PM
Author: michaelgem

Hi Bill,

Re: Something I am curious about, and don''t think it is expressed as an attack, but gotta ask you why is the avatar you selected an avatar with a wizard using a crystal ball? Rockdoc

Your question prompted me to replace the arbitrarily selected wizard avatar with this new one.

Hope it is not too disturbing. I am not good looking like Garry and Jonathan, nor can I strike an athletic pose like Wink.

Michael

Put back the WIZARD PLEASE!!! (Just a joke Michael, I just couldn''t resist it

)

And I''m glad to see that you have a sense of humor about it also, as it is NOT AT ALL "disturbing".
If people judge on solely on "looks", then they are very shallow people.

I wouldn''t post my mug because it would probably be made into a dart board somewhere in California

Or pasted on a VooDoo doll for use as a pin cushion.