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Will GIA say on CUT ?

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Yupi

Rough_Rock
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Feb 8, 2003
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74
I have read the following from a posting yesterday:

***************************************************************
AGS has loudly declared the following proportions to be "ideal" (and garnered a lot of business in the process):

Table diameter: 53-57
Crown Angle: 34 degrees to 35.5 degrees
Girdle: Thin; Medium; Slightly Thick
Pavilion Depth%: 42.5-43.5%
Culet: Pointed; Very Small; Small; Medium

The accepted industry standards for Ideal cut fall into this range. Keep in mind that ideal cuts are sometimes expressed also in terms of Pavilion Angle (the ideal is thought to be 40.75 degrees) and Total Depth (the ideal is thought to be between ~59.9% and ~63%.

It''s more complicated. The relationship of the crown angles, pavilion angles and depth% and table size vary considerably stone by stone. Symmetry relationships, minor facet lengths/percentages and other mystery factors dictate that even some diamonds which fall within the "ideal" range are not particularly stunning. GIA asserts that even AGS 5 grades can be astoundingly brilliant. See that January 1999 article. Rhino at Good Old Gold has an AGS 5 somewhere on his site which has good light return characteristics.
*****************************************************************

There was no reply after the above was posted.

Does that mean nobody agree? Experts, please provide your comment.

Anyone has the view that GIA WILL put cut details on their certs?

I personally doubt they will.

 

robbe

Shiny_Rock
Joined
Apr 24, 2003
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147
dear yupi, for years gia has been talking about cut or proportion grade. they have done neverending research on lightreturn aso...
asians & europeans have been using a simple and effective proportion chart that reflects reality for over 25 years. so why was gia unable to provide a cut grade? forget the cut grade and let me rephrase: why is the pav.depth precentage not even mentioned on a gia cert? from all measured data the pav depth is the most important as it is the pav who is responsible for return of light. how this light will be seen depends on table & crown but pav. is the most important!!!
the problem is gia is too political:
1) there is a huge market of louzy cut diamonds; by not disclosing proportion appreciation grades but only pol & sym grades, those stones will sell well.
2) gia will never launch a system invented by someone else than gia.
so they'll eventually come up with a cut grade system.
at the last gia symposium in san diego there was a 'warroom' on cut: half the attendees were against a gia cut grade and the other half was pro. i suppose that those against are used to sell louzy cut diamonds certified by gia...?
regards, robbe
 

Richard Sherwood

Ideal_Rock
Joined
Sep 25, 2002
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4,924
GIA will eventually have to come out with a cut clasification system, or they will lose their status as the premier gem laboratory of the land. This is something they will not let happen.

I personally see it happening relatively soon. They would not be spending all this time and effort researching cut if they weren't planning on producing a model soon.

When it does come out, it will probably be the best seen yet, as they have resources second to none, and seldom do things half-ass.
 

Mara

Super_Ideal_Rock
Joined
Oct 30, 2002
Messages
31,003
This is a hotly debated topic and has been discussed on here before. It's true that not all AGS 0 stones are going to be stunningly beautiful. It's true that there are non AGS 0 stones, such as AGS 5 or even AGS 7 (my stone) which can perform brilliantly.

'Cut' is made up of many factors, details, dimensions, even down to the measurements of the last facet on a stone. AGS lumped cuts into categories, for what reasons, who really knows. It was a great attempt and many feel it still holds water. But in my opinion, as an educated consumer and not related to the trade at all, the AGS scale is best taken with a grain of salt. I think the AGS scale is best used in conjunction with another tool, such as the HCA or even when paired with a phrase such as H&A. If there is an AGS 0 stone which has good pav and crown angles, and it gets a 1.1 on the HCA...I tend to think that is probably going to be a darn good stone. But if the AGS 0 is paired with a Bscope report that has only Mediums and the HCA is 4.0...then maybe that particular AGS 0 stone isnt going to be the best place for you to spend that money. If I see a stone that has AGS0 proportions and is a true H&A with the right hearts and arrows exhibited under the scope, the AGS 0 seems to gain more credence in my mind. It's not just AGS0 anymore, its AGS 0 with Hearts and Arrows. It's really very objective and is very much based on perception.

My stone is an AGS 7 with proportions that may sound odd. My appraiser, when I told her the specs (large table, shallow crown angle), said it must be a dog. When she saw it, she was shocked at how great it looked. She appraised it very well. Keep in mind that the AGS scale is 0-10 so my little 7 is closer to the dogpile than diamond nirvana. But it is a very stunning stone in person and I get many compliments on it. The shallow crown angle and depth actually combine quite well with the larger table for a great return of light. Looked pretty good under the IdealScope too. Plus it has larger spread...always a bonus!!

My 2 cents. Cut is a tricky creature indeed. There is no 'right' answer.
 

niki

Rough_Rock
Joined
Apr 22, 2003
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26
Mara,
Thanks for the post. I have an emerald cut I am looking at and it has very odd proportions as well. I have been told from several people that the "table is much to large", etc. However, I have seen the stone and it is absolutely stunning. I was very confused after looking at charts that said the cut was below average. All in all, I agree, you just have take it with a grain of salt. I'm sure that most of the time, charts can be helpful, but sometimes you just have to trust what you see.
 

Yupi

Rough_Rock
Joined
Feb 8, 2003
Messages
74
Hi everyone,

Thank you for your replies - you know, as the day goes by, and as I was reading all your replies, I could feel I am becoming more and more of an "expert" in diamonds


Anyway, thanks for all the comments, and I look forward to hearing GIA's launch of their new CUT grading !!
 

rbjd

Shiny_Rock
Joined
Feb 4, 2003
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154
I wrote the quote Yupi was referring to at the start of this thread and just to clarify, the January 1999 article reference is what I quoted in the original thread where Yupi found my post. Here are the two quotes I cited in that other thread which have citations to articles published by Professional Jeweler available on their website:

1) "The use of the term 'Ideal' is ... confusing, GIA President William E. Boyajian says.... Although it is not GIA's role to discredit the concept of an 'Ideal' cut, on the basis of our research to date, we cannot recommend its use in modern times." GIA's Brilliant Diamond Cut Study, January 1999

2) "...we are very close to answering the key questions involved in proportion evaluation for round brilliants, GIA President William E. Boyajian writes...." Study Moves GIA Closer to Cut Grade, January 2002.

I should also point out it has been over a year since GIA said they are "very close" to the "answer". I have a suspicion they have the answer but are reluctant to start using it because there is pressure on them from manufacturers and vendors not to let the cat out of the bag about how crappy some of their diamonds are. Maybe I'm too cynical, but GIA has been at this for years and hasn't made too many statements about it since the one they made 15 months ago.
 

niceice

Brilliant_Rock
Joined
Jan 29, 2003
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1,792
Even if the GIA does not want to create a cut rating system, they should provide the basic information of crown angle and pavilion angle so that consumers can make informed decisions... Failing to provide this information seems fraudulent to us... It is our understanding that the GIA does not provide this information because of political pressure placed upon them by the trade, perhaps the tide would turn if they started to receive letters from the public urging them to provide the information and letting them know that "you" decided to buy a diamond graded by the AGS Laboratory because that information was provided... $$$ has a way of "talking"...
 

Yupi

Rough_Rock
Joined
Feb 8, 2003
Messages
74
Good idea, if any group would send letters of compliant to GIA, I'll definitely join.

I also agree with adding the measurement about crown angle and pav angle and depth % of the two.

From what I've been observing the general market so far, very few people read the table and depth % shown on the GIA certs. And those who notice the existance of tables % often do not go into much detail and do not know what the numbers mean. After interacting with some of the big offline sales people, it is apparent that none of them really knows diamonds (considering I only started to learn all this not a long time ago) and they often bullsh*t a lot about the information contained in the cert.

But on the other hand I can imagine the pressure GIA faces, esp the huge market out there for bad cut diamonds......Plus not everyone is going for the "cream" cut diamond anyway, they think as long as the get a "reasonable" sparkly thing, it's alright. Because little do they know an ideal cut diamond would look "larger" visually.
 

robbe

Shiny_Rock
Joined
Apr 24, 2003
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147
dear yupi, instead of writing lettres to the gia, you may want to consider donating a few million dollars (like the mouawad family did) and then perhaps you'll have an influent voice...
check http://www.gia.edu/wd_3749.htm
regards, robbe
 

dimonbob

Brilliant_Rock
Trade
Joined
Dec 12, 2000
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670
Now GIA President William E. Boyajian and I were once both Colored Stone/Gem Identification instructors at GIA in the 70's.
GIA is going to study this cut thing to death and then do the politically correct thing. Bill has never believed in the AGS Ideal cut diamond. He is just as happy with a 60/60 diamond.
 

homer_j

Shiny_Rock
Joined
Mar 31, 2003
Messages
234
I was told today by a jeweler that the "Symmetry" category on a GIA cert encapsulated the overall proportions and quality of the cut and not just the symmetry of the facet arrangement. That contradicted what I've read here and other places, was he correct? If he was wrong, this is a perfect example as to why the GIA should include or at least clarify their grading of cut just to eliminate these confusions.
 

Garry H (Cut Nut)

Super_Ideal_Rock
Trade
Joined
Aug 15, 2000
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15,320
Actually i know cutters who believe that the stone should be within certain proportion tolerances in order to get Ex sym Rich.
For instance the girdle must be not too wide or 'thin to thick' etc.
Crown angle >35 or less than 30 would not get ex. (Those tolerances are invoked at 36 or > and 29 or < degrees BTW).

They also rather blindly follow the Sarin symmetry printout - we will be publishing something soon on that situation.

If anyone else has more to add i would like to know - I like to understand their thinking and systems.
 

Yupi

Rough_Rock
Joined
Feb 8, 2003
Messages
74
I agree with Mr. Sherwood. Because I've heard the same thing about: Good symmetry = good cut theory from one offline jeweler, which I think was rubbish.

I cannot wait to see GIA's new cut system !!!!!!
 

Richard Sherwood

Ideal_Rock
Joined
Sep 25, 2002
Messages
4,924
Garry, the symmetry grade refers to how symmetrical the finish of the diamond is. As you say, a diamond having an excellent symmetry grade will usually also have good proportions, because most cutters won't bother going through that much trouble on a diamond with lousy proportions.

The symmetry covers such things as making sure the table and culet is not off center, the girdle is not "wavy", the facets are equal sizes with their junctions lining up correctly, etc. The question of how much of an angle the crown or pavilion has doesn't fall under the symmetry category, which is why lousy proportions can exist in a stone with an "excellent" symmetry rating.

The GIA tells you to "cut the stone in half" mentally (top view, side view, bottom view), and compare one side to the other, comparing how identical they are. They also tell you to remove all your personal feelings about the proportions of the stone, because that is not what's being graded. Only the symmetry of the cut is being evaluated, not the veracity of it's proportions.
 

Octo

Rough_Rock
Joined
Apr 28, 2003
Messages
1
Hi Guys, and Gals

You guys need to see what the experts have to say on these matters.

Go to this link and all your questions will be answered regarding GIA, HRD, AGS and the rest

OCTO
 
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