Is cut grading science or opinion?

[Rockdiamond]

64%; HEIGHT: 950px" class="ibbquote">Date: 3/12/2010 12:51:35 PM
Author: oldminer
If you seek ''IDEAL'' in a fancy shape, you will NEVER select an 80% deep Princess cut over one with 65% depth, and in round brilliants you would never select one with 63% depth or more, provided the stones being examined for purchase all have equal light return and brilliancy.

The fancy one with 65% depth or the round with less than 63% depth will be SUPERIOR then, simply because they look larger than deeper stones. An overly deep stone may be a great light performer, but it falls down on the apparent size issue. This means it could NEVER BE IDEAL, if something BETTER equals its light performance and also has a better attribute, namely apparent size.

You can readily select the finest POTENTIAL cut by numbers and parameters. Right now you cannot predict which ones will give the very finest light return, but you can eliminate all the stones that will be too thin, too thick, not durable or ugly in length-to-width ratio. This is not an imaginary benefit that was dreamed up somewhere, but comes from years of grading diamonds and being interested in what other experts want and expect from the finest fancy shapes. An ugly fancy will NEVER be an IDEAL. A very deep fancy will never be a true IDEAL. A fragile stone will never be IDEAL. Too deep a stone, no matter how brilliant, is not IDEAL, Too thin a stone, no matter how large or accidentally brilliant, will never be IDEAL. There are people who do not choose to buy Ideal cut diamonds. It is up to each one of us to judge if a diamond is ugly, beautiful or somewhere in between. Calling it ''Ideal'' does not mean it is the only stone to consider buying.

IDEAL is the ULTIMATE, not simply due to a performance based on brilliancy. While brilliancy alone may be the way the general industry would like to grade fancy shapes and/or rounds, so that any diamond, no matter how poorly cut, is ''IDEAL'' as long as it is highly brilliant, this is a foolish notion. This approach would favor cutters and dealers at the expense of integrity and punish those few consumers who still have some degree of faith in diamond sellers.

IDEAL is an absolute concept of TOP QUALITY light return and cutting, and it ought to be seen as encompassing all the aspects of each stone so judged. Anything less is not really an unqualified Ideal cut. Individual consumers can buy based on their own concept of beauty, price, or any other set of parameters they choose, but only a limited number of diamonds deserve to be called “Ideal Cut” as they are near perfect in technical as well as performance specs.

The AGA Cut Class grades and the HCA for rounds provide the shape information that one adds to brilliancy information. This brilliancy information can be from Ideal-Scopes used with round diamonds, the ASET Scope and from tools such as Gemex, ImaGem or Isee2. The parametric and performance information is also part of the AGS system grading structure. This combination of expert knowledge, technical data, and science gives today’s dealers and consumers the currently best tools and information to judge or grade a diamond as “IDEAL“. No doubt we will see further technological scientific advancement in grading in years to come. I predict grading of diamonds, including cut grading, will continue to become more of a science based structure than it is today and that the trade will argue about it for many years to come. Progress or change always creates controversy.

David- it again comes down to your opinion. How could you possibly be able to state unequivocally that an "ugly fancy will never be Ideal"
Fancy shapes, by their very nature, vary due to things like corner size, and overall shape. What if AGSL gave an oval "0" cut grade, but one did not like it''s overall shape?

The term "ideal" has no agreed upon meaning unless we are referring to an AGS cut grade.
I think we can all agree that the term is one of the most misused terms in diamond advertising.

This is at the root of this discussion. It can not be "scientifically proven" that light return or optical symmetry equals beauty.
It is not true that the most brilliant round is the most beautiful to all- or even most.


What''s better, an electric heater, or a wood stove?
We can argue that the electric heater is a scientific advance, yet many will prefer the wood stove.
We could advertise that the electric heater was a scientific advance- and charge more for it.

Of course many people today will prefer the old fashioned wood stove.

What I continually see as misinformation is the effort to equate cut charts, and reflector technology to science. Then this is used to "prove" one stone is better than another.

People are saying that they can see significant difference between "super ideal" and "normal".

I agree that stones will look different based on the cut.
But who''s to say what is identified as "super ideal" will be preferred by all looking.
Furthermore, if the "super ideal" stones are more costly, wouldn''t it make more sense to advise people that this is an opinion based distinction, and that looking at diamonds may result in them picking the less costly "non super ideal"

Or we can insist that it''s "scientifically proven" that the super ideal "performs better", which is the norm here.
If education is the goal, it should also include more widely held views. I would say "alternative" but so many well thought of sellers would agree with my assessment that it''s actually not alternative.
Not to say an opinion is correct because a majority believe it- only that if education s the goal, a rounded discussion forwards that.

Can an emerald cut with 50% depth be beautiful?
If it''s "potential" we''re discussing, maybe not.
But if it''s actual stones, it might be an amazing looking diamond with great spread.

 

[Stephan]

Thank you David!
This is interesting, I was awaiting a different answer.
So this more shallow crown will only make the diamond less durable, not less beautiful.

 

[oldminer]

The AGA Cut Class is designed to denote changes in the parameters, the measurements, of all shapes of diamonds except cushion cuts. While most or many of those which perform well with light are in the top AGA grades, some are not. A diamond which is cut in some way which might be less durable or less visually large might well perform superbly with light, but I just don't think such a diamond should be called "Ideal" because there are better stones with the same light return that will be more durable and/or larger looking. Those exceptional ones should be recognized as being "better" in the overall and more of what might be called "Ideal". A 1B can still be called "Ideal", but it may be a tiny bit less ideal than some other stone. There must be a range at the top as no single set of parameters would work.

 

[Rockdiamond]

Questions for David Atlas...

Who has the right to legitimately deem stones "Ideal"? Do you think it's important for consumers to know when it's a title given by a seller, a gemologist, or AGSL?

Would you classify your AGA charts as "scientific theories" or a opinions?

 

[oldminer]

I respect the major labs in the USA to make the call for "EX" "0" or "Ideal". I don''t see many vendors, appraisers or gemologists making up their own "ideal" stands which don''t agree with those major labs.

My own AGA Cut Class charts are based on observation of actual diamonds and how I subjectively perceive the quality of cut parameters degrade as one goes from 1A down to 4B. This was based on my own experience as well as the original AGS Diamond Grading standards that are not close to today''s AGSL grading structure, GIA''s 4 classes of cut grading which was only taught in the diamond course and not used in the lab and the 3 cut categories of Rapaport which many people, even in the diamond trade, have little knowledge of. A chart based on measurements is a "fact". The grades are my considered, expert opinions and the science of today, which did not exist when I constructed these charts, appears to greatly agree with my opinions, grading structure and conclusions.

It would seem that my opinion and factually based AGA system is now in the process of being scientifically validated a bit at a time. Maybe a few improvements will be called for. Maybe it needs to be more complex. But, considering when I created these charts and rules, it was scientific for the time. Just like what was considered medical treatment in 1900 is not medical treatment today, we may see some changes, but I doubt they will be as drastic as those in medicine have been, yet medical treatment in 1900 was firmly based on the science of the times.

Science is the pursuit of truths, not just the keeper of established truth. Science changes and when it does, oftentimes once accepted "facts" are also changed.

 

[Rockdiamond]

Date: 3/12/2010 4:34:31 PM
Author: oldminer
I respect the major labs in the USA to make the call for ''EX'' ''0'' or ''Ideal''. I don''t see many vendors, appraisers or gemologists making up their own ''ideal'' stands which don''t agree with those major labs.

My own AGA Cut Class charts are based on observation of actual diamonds and how I subjectively perceive the quality of cut parameters degrade as one goes from 1A down to 4B. This was based on my own experience as well as the original AGS Diamond Grading standards that are not close to today''s AGSL grading structure, GIA''s 4 classes of cut grading which was only taught in the diamond course and not used in the lab and the 3 cut categories of Rapaport which many people, even in the diamond trade, have little knowledge of. A chart based on measurements is a ''fact''. The grades are my considered, expert opinions and the science of today, which did not exist when I constructed these charts, appears to greatly agree with my opinions, grading structure and conclusions.

It would seem that my opinion and factually based AGA system is now in the process of being scientifically validated a bit at a time. Maybe a few improvements will be called for. Maybe it needs to be more complex. But, considering when I created these charts and rules, it was scientific for the time. Just like what was considered medical treatment in 1900 is not medical treatment today, we may see some changes, but I doubt they will be as drastic as those in medicine have been, yet medical treatment in 1900 was firmly based on the science of the times.

Science is the pursuit of truths, not just the keeper of established truth. Science changes and when it does, oftentimes once accepted ''facts'' are also changed.

Unfortunately, I have seen far more examples of sellers using the term "ideal" with no basis whatsoever in "fact" as compared to the ones using it based on an agreed upon standard.
In my experience as a trader, the only widely agreed upon gemological standard of "Ideal" is a a stone graded 0 by AGSL.
IMO this is extremely important to stress to shoppers and integral to the question I asked to start the thread.
Sellers describing the cut of stones as "Ideal" without an AGSL report are using terminology that could be seen as misleading. If it''s a scientific standard, even more so.

Even if a gemologist examines a stone and feels it meets AGSL Ideal "Triple 0" standards, that''s not the same thing as a stone with the actual report.
This is the same thing as color and clarity. No matter how well respected the appraisal house, the only grades the trade will rely on are GIA or AGSL....

The closest thing to scientific standards that are agreed upon by the trade at large would be GIA and AGSL cut grades.

Reflector technology is scientific.
It is a remarkable series of inventions, along with HCA.
The results, and how they are interpreted are what takes this from a purely scientific conversation to one where the human eye is the final word.
I don''t ever see a "resolution"
If there could be an agreement overall, that might be the GIA Cut Grade- yet a lot of people have questioned stones GIA gave EX cut to- and AGS0 to a lesser degree.

 

[Dancing Fire]

RD,please tell us this....
besides using your eyes,are there certain RB "specs" you will not go beyond? in many cases (according to your eyes) a G/G stone will look just as nice as an Ex/Ex.

so,IYO...how deep is too deep,63%? 65%? how shallow is too shallow,59%? 58%?
we know you prefer big tables,but at what % would you say too big,62%? 63%?

 

[Rockdiamond]

Thanks for asking DF.

If I had to give numbers, my own personal taste would color the answer.
I feel that anything above 61% is too deep.
I prefer a stone with a slightly larger table- but above 61% would probably be a number I might use as an "upper end".
Although I prefer 60% table to 53%, I can see beauty in both.

But among the experiences that color my point of view would be the purchase of many fancy colored round diamonds.

Basically, if one is considering a pink round diamond, the selection of pinks is so paltry it makes no sense to eliminate stones without looking at them- regardless of the numbers.

This has resulted in my buying quite a few round diamonds that had numbers I never would have anticipated looking great- but somehow manage to do.

The main point here that is important to this conversation is that any numbers I would give would be based on my own taste, and experience.
Just like ANY chart made by non GIA or AGSL entities has to be viewed as the opinions of the person who wrote the chart.
Many of the charts being used here are based on the opinions of the people who wrote the charts, as opposed to hard scientific data.

GIA's grade is based on a huge amount of human observation along with other factors. Unquestionably among the most meticulous, and "scientific" research done on this subject.


If we're using GIA cut grades as a "barometer", we can see how flawed and "unscientific" the results are if we consider how many PS participants question the quality of cut of some stones which GIA did give "EX" cut grade to.

I'm actually in this group- I would not love all stones graded "EX" cut grade by GIA, and have found many stones graded "VG" cut grade that I preferred over others getting "EX"

It's important to note that GIA does not make any such claims about grading the cut of Fancy Shapes, which is far more subjective.
Can a cushion of 53% depth be desirable and considered extremely well cut by knowledgeable people in the trade?

If an "elimination tool" rejects stones that could possibly be far more desirable that ones it accepts, how good is the rejection tool?



[/i]

 

[Stephan]

Hi David, nice post.
I like your viewpoint.
Like you and Fred Cuellar (yes he sent me a free book lol), I also avoid round diamonds that have a depth higher than 61%.
But my actual diamond has a 61.7% depth and everybody loves it compared to my previous diamonds, and I can see why.
It outshines most of the things I saw before.
I had several low colored diamonds before with shallower depth.
I always remember my 59.5% depth 58% table N colored diamond - breath-ta-king fire, but it looked so yellow! I loved it but other people didn't, because of the color.
My actual diamond is an M, and I always tell people it is yellow, but they just can't see it! My guess is the edge to edge light return hides the body color.

Of course, slightly shallower diamonds can be gorgeous.
I remember of a friend who has a 57.5% depth round with 61% table, very sparkling and spready.

And I agree with you that a lot of GIA VG look better than some GIA EX.

BUT with shallow diamonds you always need an idealscope to avoid diamonds with too much obstruction.