AGA vs. AGS vs. Gia vs. what''s the deal?

[lisa1.01fvs1]

Ok, I''m confused, AGA does appraisals but their charts don''t stack up against AGS charts.

I guess there are no absolute cut standards out there?

I know that someone has posted many times the ideal parameters for RB''s (was it Ellen, Lorelei, Mrssalvo?).

How did you come by these #''s?

Sometimes my stone is AGS000/super ideal and then its 1B

and then GIA/EX/EX/EX.

Oy!

 

[niceice]

Date: 2/28/2008 1:14:07 PM
Author:lisa1.01fvs1
I guess there are no absolute cut standards out there?

There is not an industry wide accepted cut standard, but most of the trade seems to adhere closely to the parameters set forth by the AGS Laboratory, most likely because it was the first widely accepted cut rating system adhered to by the trade. Each laboratory has their own cut standard and thus there are different opinions / followings for what constitutes what in terms of cut quality.

 

[lisa1.01fvs1]

Thank you niceice.

I had a hunch but I''m glad you clarified that the trade adheres to AGS moreso (glad too b/c my stone rates well here).

I guess diamond cutting is an ever evolving entity.

 

[oldminer]

If you look way back in the history of this issue, probably five to seven years ago, AGA had a system which was very limited and strict with its 1A grade. It happened to be right in the heart of the AGS old system and still is right in the heart of the new AGS system. However, the AGA grading was for the perfectionist. It was not a commercially successful grade because few diamonds happen to hit exactly that target. Most AGS000 hit the 1B range and a few might get to 2A. I have to give credit where it is due. AGS hit on a very viable and sufficiently loose standard which does no harm to the consumer and gives the AGS Lab a business opportunity to grade the full range of the top cut diamonds as 000 cuts. The AGA 1A and 1B have the right target in mind and both grades look visibly the same. It is all in the slightest nuances.

"Standards" a little too tight are less welcomed than "standards" which are reasonably loose. "Standards" which are unreasonably loose hurt consumers, but the trade tends to use the loosest "standard" until someone makes a big deal about it. AGS Lab has nothing to worry about. They are doing a fine job with what they offer. The problem for them is how to expand beyond their role as grader of the top 5%. How many of you have ever seen an AGS111, or AGS200? I have never seen even one stone.
If AGSL and diamond dealers could figure out how to best market these other very beautifully cut diamonds, the AGS Lab could find a far larger audience. I suggest when you are looking at a GIA Ex/Ex/Ex that you convert it to an AGS and an AGA grade before you think they are all about the same. They aren't because there is no single provider, as yet, of the "standard".

 

[lisa1.01fvs1]

Date: 2/28/2008 6:04:17 PM
Author: oldminer
If you look way back in the history of this issue, probably five to seven years ago, AGA had a system which was very limited and strict with its 1A grade. It happened to be right in the heart of the AGS old system and still is right in the heart of the new AGS system. However, the AGA grading was for the perfectionist. It was not a commercially successful grade because few diamonds happen to hit exactly that target. Most AGS000 hit the 1B range and a few might get to 2A. I have to give credit where it is due. AGS hit on a very viable and sufficiently loose standard which does no harm to the consumer and gives the AGS Lab a business opportunity to grade the full range of the top cut diamonds as 000 cuts. The AGA 1A and 1B have the right target in mind and both grades look visibly the same. It is all in the slightest nuances.

Thanks Oldminer I always sit up and read your posts very carefully.

So, AGA has tougher "standards" and AGS has sort of smoothed the way for lesser perfectionism.

Out of curiosity then where are these stats in relation to AGA? I already know I have and AGS0.

6.43-6.46x3.99

ttl depth: 61.9%
table: 57%
crwn ht: 15.4%
crwn angle: 35.2 degrees
star lgth: 55%
pav. depth: 43.3%
pav. angle: 40.9 degrees
length: 75%
girdle: med-slthk

 

[lisa1.01fvs1]

http://www.gemappraisers.com/oldcutgraderules.asp

Better copy of AGA guidelines. Thanks JogiaDiamonds!

The AGS Cut Grade that is assigned to a particular diamond is the lowest grade given to any of the individual parameters. AGS also grades "Polish" and "(Facet) Symmetry" seperately using the same scale. The AGS Diamond Quality Report lists all of this information.
AGS Guidelines:

http://www.loveti.co.uk/diamond-cut.php

 

[oldminer]

There are rules of use built right into the automated cut grader which can be found linked to Pricescope right on the KNOWLEDGE section under FANCY SHAPES. The system does not simply use the lowest grade to set the grade. People refuse to read the rules, so I automated this many years back.

It is so easy to use the automated grader. The charts are the underpinning of the grading, but not the exact way the grade is generated. There are degrees of "" built in for Sarin/Ogi error, human inability to measure and tolerance for very slight variations which can''t be eliminated. Please use the automated grader or read the rules closely.

Any proferssional or interested amateur can download the automated system for free as a virus free, zipped file, on my previous business'' website, www.gemappraisers.com. Left side of the homepage.

 

[lisa1.01fvs1]

Thanks Oldminer - I am sorry you had to point out the DIY test - quite the overload here.

According to the automated grading I scored 1B

crown angle was the "setback"

Question for you --does 1 degree matter that much for the crown angle?

(I have 35.2 and AGA cuts off 1A at 35.1)?

I know I have OCD

 

[oldminer]

Everything matters! The entire business of diamond grading is the splitting of fine hairs. We sort of enjoy the project and urge all comers to come split hairs with us. Every system has artificial borders drawn by their creator. There are gray areas at borderlines. The more gradations, the more borderline calls. Rough grades, with few gradations, have less borderline calls, but way less potential value or accuracy. A 1B is going to be a superior cut diamond AND an ideal cut one, too. I view this as a great outcome and not at all a problem. 1B is the Bull''s Eye and 1A is dead center of the Bull''s Eye. 1A never made the impact in the general market because it was viewed as virtually unobtainable. My own wife wears a 2A round which she happens to be very happy with. It is amazing how a good sized diamond makes cut grading a little less crucial to my in-house expert.

 

[lisa1.01fvs1]

Oldminer, now you are making me think YOU are the "Bobby Fisher" of diamonds!

Sorry strmrdr, Garry..

Have you guys ever duked it out?

Hmmm...the HCA. The AGA. The AGS, The GIA, The CIA..........losing my mind

BTW: what size if your wife''s rock?

Lisa