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Question about using the AGA grading chart

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ifeelsoalive

Rough_Rock
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Jan 29, 2003
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1
I had a question about how one should interpret the AGA grading chart.

1B grade:
All characteristics need to be all 1B or 1A to 2B. Only a single class 2 characteristic is permitted. The class 2 characteristic should be within 2% or 2 degrees of the 1B characteristic.

My question is: does the 2% mean + or - 2% or 2% of the value.

for example: if the crown height is 6.5% for a princess cut diamond but the rest of the measurements for into the 1a or b category, is the diamond considered a 1b AGA? 6.5 + 2 = 8.5% (falls under 1b) or is it a 2b AGA? 6.5% x 1.02% = 6.63%

Thanks!
 

RockDoc

Ideal_Rock
Joined
Aug 15, 2000
Messages
2,509
For fancy shapes the proportions are not predictable with any degree of accuracy.

I have seen stones with "rotten numbers" look great and stones with 1a proportions not look so great.

Fancy shapes MUST BE SEEN to assess their performance.

Rockdoc
 

oldminer

Ideal_Rock
Trade
Joined
Sep 3, 2000
Messages
6,356
I always treat any questions posed to RockDoc with deference. I expect the same treatment in return...

If you or anyone else have specific questions about using the AGA-Cut Grade rules, please let me know and I will try to give you answers that make sense, not just a negative reply.

In your case the 2% means a variance from one reading up to 2% more or less. So if we take the best reading as 12%, then you have a range down to 10% or up to 14%. I know it could be otherwise interpreted, but it is difficult to express the way this works in words sometimes.

I do want you to know that cutters are not dopes. If they cut a 1A stone that looks poorly it is not because of my "faulty" cut grading system, but the fact that this cutter is not a very good cutter. The more experienced cutters now can create really super looking 1A cut fancies now that they are defined combined with their many years of cutting skill. When anyone tells you they just saw a lousy looking 1A or 1B cut diamond, they are looking at either a failed attempt to do a good job, a difficult stone that resisted normal cutting techniques, or a mistake. Good cutters make wonderful AGA 1A, 1B and 2A fancy shapes.
AGA Cut Class grading when compared to the very best looking fancy shapes just happen to match up very nicely. It is not just an accident but it is fine cutting skills combined with the ability to see the aesthetically pleasing shape of the cut desired.

That's what the AGA Cut Class is all about. Fine cutting skill and great shaping combined..... You cannot grade the potential appearance of a fancy shape diamond solely by numbers and charts. However, the potential for ultimate beauty is highly doubtful below the 2A AGA Cut Class...That ought to be very helpful to many consumers.

I have always asked for constructive advice or evidence of error in the cut grading we do. So far, I have had very little advice. Something there must be just about right as this information has been in place for over ten years with only very slight revisions during that time.
 

RockDoc

Ideal_Rock
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2,509
Dave........

First off ... my reply is NOT personal towards you and was not meant to be disrepectful or unprofessional.

I don't quite understand your reply saying that if a stone is a 1A on your chart, and the stone doesn't perform it is the fault of the cutter and not the chart.

Let's take princess cuts as an example. The pavilion of the princess cut is divided into four quadrants. The quadrants need to be equal, and the culet needs to be centered in order to establish even light return and eliminate dead areas.

The overwhelming majority of princess cut are not cut with exacting quadrants.
Of course, if a cutter does cut an "off balance" stone, yes in part its the cutter's fault that the stone doesn't perform, but then the chart doesn't seem to address these additional charactersitics that can seriously affect the appearance and light return performance.

Again, I revert to how important it is to NOT use averages, and to evaluate the diamonds based on their actual angles and lengths.

Let's talk generally about fancy shapes too..... in that there isn't a standard that totally, accurately and comprehensively analyzes angle standards ( particularly for pears, oval and marquises), where the angle steepen and shallow out around the stone, you chart doesn't and hasn't addressed these issues.

While considering only a portion of the facets (which AGS does) does not provide a really accurate evaluation of cut or performance. IF the cutter can get away with leaving extra weight on a stone, due to the inadquacies of the grading system, then what do we "fix" the grading system or the cutter? To me, the obvious and patently obvious reason is the cut grading system. As once, this information is more properly and accurately made and shared with purchasers, the cutters will adjust their "habits" accordingly.

These are plain and simple facts which many chose to ignore. As such, consumers can "think" their getting a great stone, when in fact they MAY not.

My intent was not to insult you, but rather to share the information in the hopes that the current system will be improved. I certainly realize that this is a huge and very difficult undertaking, as the rest of the proportions would have to be re-calculated to also deal with every degree of length width ratio as well. How about grain orientation? Don't you think that affects light refraction?

What about facet placement? This is paramount to a fancy shape's performance as well. Is this addressed in the AGA analysis?

I certainly welcome improving the systems out there. I encourage you to do so too. That is the basis and reason behind my postings.

I certainly also understand and acknowledge that some of this is up to mother nature and not gemologists...Due to the variances of stones, I am not sure we can ever have a chart system that will accurate predict and relate to light return.

Rockdoc
 

Richard Sherwood

Ideal_Rock
Joined
Sep 25, 2002
Messages
4,924
-----------
Again, I revert to how important it is to NOT use averages, and to
evaluate the diamonds based on their actual angles and lengths.
-----------

While I agree with you that fancy shapes have to be seen to be evaluated, I find the AGA charts to be a useful tool in pointing the internet consumer in the right direction toward purchasing a good looking stone, while at the same time warning them of stones which might have a problem.

The vast majority of time a stone placing in the 2B rank or better is going to look pretty darn good. This is not to say that a 3A, 3B, or even sometimes a 4A won't look good, but the chances are that the higher a stone places on the scale the better it's going to look.

With the new market of the internet in full swing, tools like the AGA Cut Class system are a tremendous help to the consumer. Consumers are often clueless, and the AGA scale definitely gives them a clue as to some major things to look for in cut.

If savvy Internet vendors then augment this with things like IdealScope & Brilliance Scope images, the consumer has a reasonable chance of making an intelligent decision regarding cut.
 

RockDoc

Ideal_Rock
Joined
Aug 15, 2000
Messages
2,509
----------------
On 1/30/2003 9
2:28 PM Richard Sherwood wrote:

-----------
Again, I revert to how important it is to NOT use averages, and to
evaluate the diamonds based on their actual angles and lengths.
-----------

While I agree with you that fancy shapes have to be seen to be evaluated, I find the AGA charts to be a useful tool in pointing the internet consumer in the right direction toward purchasing a good looking stone, while at the same time warning them of stones which might have a problem.

The vast majority of time a stone placing in the 2B rank or better is going to look pretty darn good. This is not to say that a 3A, 3B, or even sometimes a 4A won't look good, but the chances are that the higher a stone places on the scale the better it's going to look.

With the new market of the internet in full swing, tools like the AGA Cut Class system are a tremendous help to the consumer. Consumers are often clueless, and the AGA scale definitely gives them a clue as to some major things to look for in cut.

If savvy Internet vendors then augment this with things like IdealScope & Brilliance Scope images, the consumer has a reasonable chance of making an intelligent decision regarding cut.


----------------
Richard.... while I appreciate your response, my point is if experts provide methods of comparison, where the consumer expects that if the stone is a 1a its the cat's meow of cutting, then that is what they should get.

Using the FireScope, Brilliance Scope and Sarin reports all examine the stone itself. The items that don't actually see the diamond cannot provide accurate detail for a particular diamond.

The question here is Do Consumers want information that they can safely and accurately make their purchasing decision with complete information or do they want as you stated "just a reasonable chance".

Read through the forums and see how many consumers have place total reliance on the performance of a diamond using the HCA. As an initial sort tool the HCA is certainly useful for picking a stone that should be checked out in person by an expert, but many consumers are basing a high degree of reliance upon the results - results that when only part of the data is considered makes having a high degree of reliance skewed.

It's very easy for someone who's money isn't at stake to say it doesn't matter, the averages are good enough.....but we should all have realized that this is not complete or comprehensive enough. My thrust here is to encourage improvement in the tools so that more conclusive and correct results are made - not to badmouth anyone.

My reason in bringing this out is to encourage those who do have such "tools" to improve and make them better and provide information and results that are more reliable to the person actually putting up the $$$$.

Incidently, Richard, what percentage of princess cuts do you think are actually equal in the pavilion quadrants ? How wide should the chevrons be at the widest point? What should be the range of crown angle ?

Rockdoc
 

Richard Sherwood

Ideal_Rock
Joined
Sep 25, 2002
Messages
4,924
-----------
Incidently, Richard, what percentage of princess cuts do you think are
actually equal in the pavilion quadrants ? How wide should the
chevrons be at the widest point? What should be the range of crown
angle ?
-----------

Why don't we just both whip it out and see who's is bigger...

Heh heh heh...
 

oldminer

Ideal_Rock
Trade
Joined
Sep 3, 2000
Messages
6,356
RockDoc;

I never hold a grudge and certainly do not view your continued responses anywhere in the thread offensive to me. No problem!!! I know you speak your mind and really want to see consumers satisfied and well treated. That's a big goal we share. The give and take of information is welcomed by everyone.

I will reword my thoughts on why one cannot always rely on AGA or other charts and specs to know how a fancy will "look". I have seen fine looking 1A princess cuts in recent months because some smart cutters have finally figured out how to make a reasonably spready princess that also looks super. In past years I saw many failed attempts that may have fit the 1A or 1B parameters, but were downright ugly. The combination of cut choices just was not yet worked out. Those were failed attempts by cutters working on a solution that has now been found by a limited number of skilled cutters. More will follow, given time.

There are some very good looking 2A and 2B and even 3A princess cuts, but I'd promise you they are generally more deep than necessary and therefore do not give the utmost size appearance for the money being spent. They are a little like steak with too much fat. You pay by weight, but you only want to eat the meat. There is waste and the price for an untrimmed steak ought to be lower than for a properly trimmed one. In some sense this analogy applies to Fancy shapes, too. Just don't eat one!!!!

The AGA-Cut Class charts are a well developed system for judging the cut skill of the cutter WHEN the diamond has a great look. One must use their eyes to make that determination. When you have a lower cut grade, the diamond may look okay, but there are ways that could have been employed to make it even better. That is what the AGA system is all about. Making the cutter realize that good enough is not always "the best".

For years we suffered with every fancy being touted as a "fine cut" because of no standards. Now, we have some standards in place that work to improve cutting and appearance. This is not an end, but a beginning point of total brilliancy and cut grading combined. A diamond with a 1A or 1B cut grade and a very high BrillianceScope score will definitely be a super performer and a well cut stone.

I hope that this makes perfect sense to all.
 
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