Do princess cuts get a "cut" grade from GIA?
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JohnQuixote
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Short answer: No.
Longer answer: GIA cut grading is proportions-based. This works for rounds, which have he variables in different princess configurations are much more complex so a proportions-based system does not work. The AGS does offer cut grading for fancy shapes with a 3-dimensional system (elaborate info here). It it very strict though, and few diamonds are sent there as most will not qualify for the top cut grade.
You can find top-cut diamonds with GIA reports (they''re the preeminent lab in terms of global reputation) but to predict cut quality sight-unseen you will need to have an ideal-scope or (preferably) an ASET image - or other proof of performance - and/or work with a trusted expert who has the diamond in-hand.
Longer answer: GIA cut grading is proportions-based. This works for rounds, which have he variables in different princess configurations are much more complex so a proportions-based system does not work. The AGS does offer cut grading for fancy shapes with a 3-dimensional system (elaborate info here). It it very strict though, and few diamonds are sent there as most will not qualify for the top cut grade.
You can find top-cut diamonds with GIA reports (they''re the preeminent lab in terms of global reputation) but to predict cut quality sight-unseen you will need to have an ideal-scope or (preferably) an ASET image - or other proof of performance - and/or work with a trusted expert who has the diamond in-hand.
Regular Guy
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Alleycat,
GIA doesn''t grade for cut outside of rounds. AGS does.
Smart guys here seem to have ideas about how to judge performance based on certain proportion parameters. Either read a lot of threads to get this down...or consider shopping AGS for their 0...they do grade these.
GIA doesn''t grade for cut outside of rounds. AGS does.
Smart guys here seem to have ideas about how to judge performance based on certain proportion parameters. Either read a lot of threads to get this down...or consider shopping AGS for their 0...they do grade these.
Regular Guy
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Alleycat,
As JQ says, no, you especially for fancies (non-rounds) use with any reliability proportions too well. This tries...and does take a whack at it (you''ll see several shapes covered there)...but...for example...AGS cherry standards I think don''t map onto Dave''s charts...and so you don''t even have alignment, let alone consistency in suggestions.
As JQ says, no, you especially for fancies (non-rounds) use with any reliability proportions too well. This tries...and does take a whack at it (you''ll see several shapes covered there)...but...for example...AGS cherry standards I think don''t map onto Dave''s charts...and so you don''t even have alignment, let alone consistency in suggestions.
From the Accredited Gem Appraisers site http://www.gemappraisers.com/oldcutgraderules.asp. Someone else linked it on another post...
I just got this chart below from a dealer when they sent me some stones to peruse. I had asked her about the rule that the table should be less than depth and she said that that wasn''t necessarily true all the time. Seems like it''s a little bit liberal and also doesn''t mention anything about proportions. Can anyone comment? Thanks!
You are most welcome. When considering an Ideal princess cut diamond, the preferred proportions are as follows:
Depth: 54.0% - 75.0%
Table: 59.0% - 72.0%
Polish: Good to Excellent (Or AGS Ideal)
Symmetry: Good to Excellent (Or AGS Ideal)
Girdle: Thin to Thick
*Any variation when considering girdle % is acceptable. What you want to stay away from are the extremes such as Extremely Thin to Extremely Thick.*
I just got this chart below from a dealer when they sent me some stones to peruse. I had asked her about the rule that the table should be less than depth and she said that that wasn''t necessarily true all the time. Seems like it''s a little bit liberal and also doesn''t mention anything about proportions. Can anyone comment? Thanks!
You are most welcome. When considering an Ideal princess cut diamond, the preferred proportions are as follows:
Depth: 54.0% - 75.0%
Table: 59.0% - 72.0%
Polish: Good to Excellent (Or AGS Ideal)
Symmetry: Good to Excellent (Or AGS Ideal)
Girdle: Thin to Thick
*Any variation when considering girdle % is acceptable. What you want to stay away from are the extremes such as Extremely Thin to Extremely Thick.*
Thanks for all the info everyone I greatly appreciate it. Do you know how sites like Blue Nile or James Allen (or any online store) determine which princess stones fall into their "ideal cut" category. I just hate the idea of rolling the dice when it comes to cut!
Regular Guy
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Consider investing in an AGS certed option?
Betting both BN & JA defer to the chart referred to by both me & JJ970.
Also...see that BN regards AGS0 options as only good cuts....i.e., they are not really trying to figure it out.
JohnQuixote
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Such a list is not useful for selection. Many sellers have their own interpretation of ideal. Most will be nowhere as strict as AGS Ideal, and may actually be pretty loose. Numbers like the above are meaningless except as a potential filter to narrow things down, and no guarantee of that: There are configurations meeting the above criteria above that are terrible performers, just as some may be wonderful.
Because of the variables involved it is impossible to judge the light performance of a princess cut using proportions. When using a list of numbers like the above, or the AGA lists, it is no more than a potential filter. A fancy shape must be seen firsthand for a decisive evaluation.
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We now have ImaGem based direct measurement of light behavior available for princess cut diamonds. While this technology has been slow to be adopted, it is working well. EGL USA has adopted it for their new 360 degree report which they are marketing now in its early stages. At AGA we have had this technology for a couple years just waiting for the market and the needs of consumers to catch up with the latest advances. The ImaGem process takes into account the quality of light return, the cut, regardless of parameters. AGS 0 princess cuts score over a rather wide range, but so do the best of non-AGS well cut princess cuts. Much of the business is determined by your own personal preference, but you can find out a lot today with technology that was not around a few years ago when I worked up the AGA Cut Class system based only on parameters.
No matter what lab has graded your princess cut, we can add on a Light Behavior only measurement with objective and repeatable results. It is just one more tool to assist consumers in making a "best" choice, but still leaves the final choice in their hands. A gemologist may have an opinion about whioch diamond looks best when one is fair and the other is excellent, but the determination of best beauty in two finely cut similar diamonds is pretty much going to be a subjective call best made by an informed consumer.
No matter what lab has graded your princess cut, we can add on a Light Behavior only measurement with objective and repeatable results. It is just one more tool to assist consumers in making a "best" choice, but still leaves the final choice in their hands. A gemologist may have an opinion about whioch diamond looks best when one is fair and the other is excellent, but the determination of best beauty in two finely cut similar diamonds is pretty much going to be a subjective call best made by an informed consumer.
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You are absolutely right, John, it is incorrect to use such simple rules as above.
I would say even more, and add that going out of the abovementioned parameters can make an AGS-0 stand out positively in the company of other AGS-0''s. It is part of the light return that is observed by humans, but which is neglected in the AGS'' quantification of light return.
In the same way, no ''direct measurement tool'' like Brilliancescope or Imagem can offer correct results, because it misses in its quantification a very important aspect, which human observers value.
The ASET-view of the stones however clearly shows this difference.
I am working on an article about this, but I do not seem to succeed in making it easy to read. Tomorrow, we hope to hire a ''Communications Manager'', and she hopefully can assist me in molding this observation into a clearly readable article.
Live long,
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Paul: Imagem went out of their way to take HUMAN OBSERVATION into account in the grading strategy. We ran real human grading tests. To not know about a technology is excusable, but to criticize without knowledge, is not a good thing.
Why not really give the Imagem grading a test to see if it meets your observed results. Your input would be welcomed regardless of the outcome as you are highly respected for your advancement of the cutting business from the practitioner''s point of view. I would be pleased to grade as many diamonds as you might wish to have results on, especially AGS 0 princess cuts, providied you''d let me publish the results, good, bad or in between. Any other sellers of top make princess cuts are also welcome with the same release to publish the results. WF, GOG, are you there? Many great stones are out there which I''d sure love to measure and examine more closely. No doubt, consumers would like to know more on this topic, too.
In the end, the customer decides what to buy based on personal taste and budget. No system should dictate which is "best" except within a rather broad range of top performance. I believe all the best systems are doing this, but some system may work best and few folks want to test which one at this point for fear their chosen system might not be the one that proves most accurate.
Why not really give the Imagem grading a test to see if it meets your observed results. Your input would be welcomed regardless of the outcome as you are highly respected for your advancement of the cutting business from the practitioner''s point of view. I would be pleased to grade as many diamonds as you might wish to have results on, especially AGS 0 princess cuts, providied you''d let me publish the results, good, bad or in between. Any other sellers of top make princess cuts are also welcome with the same release to publish the results. WF, GOG, are you there? Many great stones are out there which I''d sure love to measure and examine more closely. No doubt, consumers would like to know more on this topic, too.
In the end, the customer decides what to buy based on personal taste and budget. No system should dictate which is "best" except within a rather broad range of top performance. I believe all the best systems are doing this, but some system may work best and few folks want to test which one at this point for fear their chosen system might not be the one that proves most accurate.
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Not only..., the paper (grading reports) are a significant part of the equation..., which takes a lot of the subjectivity of "personal taste" out of the equation...
Didnt get that one..., can you elaborate a bit, please?
We are talking about a fancy shaped Diamond..., right?
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"except within a rather broad range of top performance"
This means that there is far more than one and only one cut type for any shape which is in the best category. GIA has "Excellent" for rounds of quite diverse cutting result and light behavior. They have been criticized for this looseness although diamond sellers are sure to take advantage of the range possible within the top GIA cut grade. The AGS is recognized as tighter on its top "0" cut grade. Dealers who offer those stones tout their relative scarcity and gain a bit of a premium in price. However, we know that not every AGS 0 looks the same as every other. There is still a range of what is in the best category. Imagem has followed the pattern of categorization accepted by the industry. Not every diamond graded Excellent+ will be identical but all will have highly pleasing attributes of beauty.
What I do have some evidence of is that the range of GIA "excellent" in round diamonds is very broad compared to AGS 0 and the these two systems both seem broad compared to the categories supported by Imagem technology which find AGS 0 and GIA "Excellent" cuts ranging on the Imagem scale from as low as "good to as high as "excellent+", a five grade spread.
There is very little market for even AGS 1 cuts and even less for AGS 2 cuts, so when a dealer has such stones the tendency is to use GIA or some other lab. Using a different lab alows buyers seeking a compromise in cut to afford the diamond they wish to purchase, but it has limited the broad acceptance of AGS graded diamonds into the more commercial stone arena. This limits the business AGSL can do.
The Imagem grading model defines performance with tighter categorization. I believe it does a better job of separating actual, measured performance, from what can be visually appreciated. A top grade Imagem result is not visibly different than a category lower, but at the two category spread, there is a visual difference to an astute observer. Some diamonds once considered non-ideal makes can do quite well with Imagem light measurement since it does not consider parameters.
However, the consumer is the ultimate judge of beauty, size, color, clarity, and budget. The goal, as I see it, is to provide factual data to foster a full decision making process which ultimately is not in my hands, but in the hands of my clients.
This means that there is far more than one and only one cut type for any shape which is in the best category. GIA has "Excellent" for rounds of quite diverse cutting result and light behavior. They have been criticized for this looseness although diamond sellers are sure to take advantage of the range possible within the top GIA cut grade. The AGS is recognized as tighter on its top "0" cut grade. Dealers who offer those stones tout their relative scarcity and gain a bit of a premium in price. However, we know that not every AGS 0 looks the same as every other. There is still a range of what is in the best category. Imagem has followed the pattern of categorization accepted by the industry. Not every diamond graded Excellent+ will be identical but all will have highly pleasing attributes of beauty.
What I do have some evidence of is that the range of GIA "excellent" in round diamonds is very broad compared to AGS 0 and the these two systems both seem broad compared to the categories supported by Imagem technology which find AGS 0 and GIA "Excellent" cuts ranging on the Imagem scale from as low as "good to as high as "excellent+", a five grade spread.
There is very little market for even AGS 1 cuts and even less for AGS 2 cuts, so when a dealer has such stones the tendency is to use GIA or some other lab. Using a different lab alows buyers seeking a compromise in cut to afford the diamond they wish to purchase, but it has limited the broad acceptance of AGS graded diamonds into the more commercial stone arena. This limits the business AGSL can do.
The Imagem grading model defines performance with tighter categorization. I believe it does a better job of separating actual, measured performance, from what can be visually appreciated. A top grade Imagem result is not visibly different than a category lower, but at the two category spread, there is a visual difference to an astute observer. Some diamonds once considered non-ideal makes can do quite well with Imagem light measurement since it does not consider parameters.
However, the consumer is the ultimate judge of beauty, size, color, clarity, and budget. The goal, as I see it, is to provide factual data to foster a full decision making process which ultimately is not in my hands, but in the hands of my clients.
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"Imagem is saying or showing you dont need an AGS-0" to be a "top-performer or GIA triple EX to still have a great Diamond with great "light measurements" or performance?"
I have edited your quote with the addition of "to be a" for clarity purposes.
Garry Holloway has been telling us for years exactly the same thing. The Ideal-Scope and ASET Scope do not care about parameters, but use simple direct assessment with our eyes as the discriminators. GIA has found a wide range of parameters for what they consider the best cut. AGS has found that their old parametric system did not properly cover all the best performance and has vastly revised their outlook. Everyone is saying that some lovely, high performance diamonds lie outside of the once tradional, expected parameters.
I am also still saying that parameters are good screening tools, but can't possibly compete with direct measurement tools. So many, nearly an infinite number, of potential parametric mixes can be cut and we simply will never invest in enough programming to do more than roughly predict light behavior. It seems unrealistic to promote prediction of the light behavior when tools exist which measure it directly. This is why I sell I-S, ASET and promote ImaGem. No grading system in the entire world uses predictive measure when direct measure is available. Anyone who can give an example of such prediction being used in place of direct assessment for "grading" ought to give the example they know of. I have asked many times, but no one has stepped up with an example. I am told that none exists, but am open to new information.
I have edited your quote with the addition of "to be a" for clarity purposes.
Garry Holloway has been telling us for years exactly the same thing. The Ideal-Scope and ASET Scope do not care about parameters, but use simple direct assessment with our eyes as the discriminators. GIA has found a wide range of parameters for what they consider the best cut. AGS has found that their old parametric system did not properly cover all the best performance and has vastly revised their outlook. Everyone is saying that some lovely, high performance diamonds lie outside of the once tradional, expected parameters.
I am also still saying that parameters are good screening tools, but can't possibly compete with direct measurement tools. So many, nearly an infinite number, of potential parametric mixes can be cut and we simply will never invest in enough programming to do more than roughly predict light behavior. It seems unrealistic to promote prediction of the light behavior when tools exist which measure it directly. This is why I sell I-S, ASET and promote ImaGem. No grading system in the entire world uses predictive measure when direct measure is available. Anyone who can give an example of such prediction being used in place of direct assessment for "grading" ought to give the example they know of. I have asked many times, but no one has stepped up with an example. I am told that none exists, but am open to new information.
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