Clarity standards vary with Weight / Size

[oldminer]

Many of you might not realize that the GIA clarity system makes subjective adjustments for the amount of inclusions and blemishes depending on the size of the diamond. As stones increase in size, the grading may appear to liberalize. Diamonds of 4 carat might have visible inclusions that would be graded I1 in a carat size stone, yet only grade SI1 in a 4 carat stone.

Major lab employees are gradually trained to make these adjustments over time. The GIA course of study most gemologists in the USA have followed really deals with diamonds of 1/2 carat and less in weight. As soon as we are thrown into the real world, we start to grade 1 and 2 carat diamonds where the clarity grading GIA has given these larger stones seems ultra-liberal to the unitiated, new gemologist. Some gemologists never seem to learn how to make this adjustment. Others go the other extreme and lose perspecive on how liberal grading can be. Some gemologists want to make fixed standards, but they are not in a position to create standards at all. Standards arise because of a real consensus, not an individual position arbitraily chosen.

The GIA occasionally makes some attempt at what they call "Advanced Clarity Grading" in classes or lectures. Really, it is not in their own best interest to tell us what the policy of the Gem Lab is. It could cost them business. However, they do let on to those who are paying attention that the standards do vary as size / weight increases.

The point? You must expect some surprises wityh clarity grading. You can be surprised by GIA or other well accepted trade reports. You can also be surprised by most any other gemologist''''s opinion of clarity. This is a different sort of problem that color grading. Many consumers can''''t see any of the inclusions that set these grades. At least with color grading, most can detect some nuance of color variation. Expect the unexpected! Some appraisers feel they have the key to grading clarity properly. Other may admit it is not easy to make the adjustments for size that major labs deal with on a daily basis. We prefer to think we work on it and keep it in mind while we examine larger stones. Knowing how the big guys do their work and making the attempt to come close to their grading style and philosophy is an ongoing task. Believing that clarity grading is a yardstick that never varies can get you into a lot of trouble.

 

[Gonzodogg]

This is why I love Pricescope.
Info like this is so interesting to me.

 

[Lorelei]

Thanks for that Dave. I remember reading a story of Jons that when he was in a clarity grading class, the lecturer showed a picture of a large emerald cut and asked the class what they would grade it at. They all said I1 but it was actually a VS, in such a large diamond ( I think it was about 9 carats or so) the inclusions may be eye visible even in a higher clarity. It is a good point to bring up as it can be confusing at times!

 

[strmrdr]

If I was in the mood for a storm rant it would contain the F word and not the fu word but the Fr one that isnt France.

 

[f0rbidden]

wow. I didn''t realize that, but the more I think about it, the more logical it seems.

Thank you for sharing this VERY valuable information!

 

[MissAva]

Date: 4/6/2006 9:06:28 AM
Author:oldminer
Many of you might not realize that the GIA clarity system makes subjective adjustments for the amount of inclusions and blemishes depending on the size of the diamond. As stones increase in size, the grading may appear to liberalize. Diamonds of 4 carat might have visible inclusions that would be graded I1 in a carat size stone, yet only grade SI1 in a 4 carat stone.

Major lab employees are gradually trained to make these adjustments over time. The GIA course of study most gemologists in the USA have followed really deals with diamonds of 1/2 carat and less in weight. As soon as we are thrown into the real world, we start to grade 1 and 2 carat diamonds where the clarity grading GIA has given these larger stones seems ultra-liberal to the unitiated, new gemologist. Some gemologists never seem to learn how to make this adjustment. Others go the other extreme and lose perspecive on how liberal grading can be. Some gemologists want to make fixed standards, but they are not in a position to create standards at all. Standards arise because of a real consensus, not an individual position arbitraily chosen.

The GIA occasionally makes some attempt at what they call ''Advanced Clarity Grading'' in classes or lectures. Really, it is not in their own best interest to tell us what the policy of the Gem Lab is. It could cost them business. However, they do let on to those who are paying attention that the standards do vary as size / weight increases.

The point? You must expect some surprises wityh clarity grading. You can be surprised by GIA or other well accepted trade reports. You can also be surprised by most any other gemologist''s opinion of clarity. This is a different sort of problem that color grading. Many consumers can''t see any of the inclusions that set these grades. At least with color grading, most can detect some nuance of color variation. Expect the unexpected! Some appraisers feel they have the key to grading clarity properly. Other may admit it is not easy to make the adjustments for size that major labs deal with on a daily basis. We prefer to think we work on it and keep it in mind while we examine larger stones. Knowing how the big guys do their work and making the attempt to come close to their grading style and philosophy is an ongoing task. Believing that clarity grading is a yardstick that never varies can get you into a lot of trouble.

But why, the inclusions are either visible or they aren’t... This does not follow their little own definitions.

 

[valeria101]

Quick question ...


What exactly are these grades good for anyway ?

 

[strmrdr]

Date: 4/6/2006 9:47:55 AM
Author: valeria101



Quick question ...



What exactly are these grades good for anyway ?

serving the trade.......

 

[valeria101]

Great, of course... whatever. But then, why do buyers need to know about them?

 

[klavigne]

So Dave,
It would seem that what you are telling us is that inclusions are graded based on the percentage size of said inclusions? So with a larger diamond you really need to be in the higher range to have an eye clean stone? So a 5 carat VVS1 could possible have the same "percentage" of inclusions as a 1carat SI1? Or said differently, if the 5 carat stone has a 5 micron inclusion and the 1 carat had a 1 mircon inclusion, they wouldn''t be graded the same? Is that the jist of this? I guess it all really does make sense if stated this way.

 

[valeria101]

Date: 4/6/2006 10:52:19 AM
Author: klavigne

So a 5 carat VVS1 could possible have the same ''percentage'' of inclusions as a 1carat SI1?

It ain''t that bad! There''s a a long laundry list of grading rules, not just ''mass of inclusions / mass of diamonds'' - ''wish it was a simple rule

In fact, I wonder why these grading rules cannot be transparent. Maybe most buyers would never care to look into them, but it doesn''t look like small transparent rocks are such an intricate object that it should take a lifetime of toil to understand what they are all about. The human activity around them might be that way, but these grades should be about the rocks, right ?

 

[strmrdr]

Date: 4/6/2006 10:17:00 AM
Author: valeria101



Great, of course... whatever. But then, why do buyers need to know about them?

because it sets the price.
Which is why this is a bad thing.
It also isnt how GIA defines it on their website .. wonder why.....
Combine this with the grading practice of grading a chip for large diamonds and the conclusion has to be that large diamonds are being over graded to bring higher prices.

 

[valeria101]

Oh well.. it was pretty much a rhetorical Q Strmdr.

You know, there is a saying that ''talk is cheap''. Well, definitely not this sort of talk!

 

[oldminer]

The GIA teaches gemologists to grade small diamonds. Just like when we first learn small words and then grow into more complex spelling and sentences. The truth is that experience is left to teach most of us how grading of larger diamonds is done. There is no universal definition of where an inclusion becomes eye-visible except for the definition GIA uses when teaching about small diamonds. The way it reads one could easily be mislead into believing the rule was a general rule, when it clearly is not the way the GIA Gem Trade Lab does its work.

There is no simple stated relationship of inclusion percentage to grade or to size, but there is an implied adjustment based on size of the diamond. Grading is subjective and the grading of larger, more expensive diamonds is even more subjective. Since few teachers of the subject are available one is left to work it out over time. As the value and size increase the risk and subjectivity range also seem to increase.

About 20 years ago I wrote an article for the Accredited Gemologists Association Newsletter asking if it was time for a fixed set of clarity standards. I offered up the thought of adding a clarity grade like SI3 long before such a grade became a reality, but the concept I had was to fix standards to grading, not just add a larger dimension to the subjective confusion. The trade chose to add confusion and not fix the situation. Many of us certainly can understand who runs the show and why they chose that course. I figure there is still time left to fix things for the better.

 

[canuk-gal]

Date: 4/6/2006 1:21:44 PM
Author: oldminer

Grading is subjective and the grading of........

HI:

If this doesn''t say everything, at least it explains a lot.

cheers--Sharon

 

[Madam Bijoux]

Which is why clarity should be the least of anyone''s worries.

 

[Modified Brilliant]

Standards arise because of a real consensus, not an individual position arbitraily chosen
-------------------------------------------------------------------------------------------------------------------------
Dave,
It is understood by most gemologists/appraisers that more "liberal" grading does in fact take place with larger diamonds.
I learned this from a long time diamond merchant when I was just starting out in the biz.
Could you please define "consensus?" Are you referring to the diamond manufacturers, wholesalers, labs or the jewelry industry as a whole?
Thanks.

www.metrojewelryappraisers.com

 

[Dancing Fire]

Date: 4/6/2006 9:42:51 AM
Author: Matatora

Date: 4/6/2006 9:06:28 AM
Author:oldminer
Many of you might not realize that the GIA clarity system makes subjective adjustments for the amount of inclusions and blemishes depending on the size of the diamond. As stones increase in size, the grading may appear to liberalize. Diamonds of 4 carat might have visible inclusions that would be graded I1 in a carat size stone, yet only grade SI1 in a 4 carat stone.

But why, the inclusions are either visible or they aren’t... This does not follow their little own definitions.

but... it does make sense.do you really expect to see a 5 ct SI1 stone with the same size inclusion as a 1 ct SI1?

 

[strmrdr]

Date: 4/6/2006 7:14:10 PM
Author: Dancing Fire

Date: 4/6/2006 9:42:51 AM

Author: Matatora

Date: 4/6/2006 9:06:28 AM

Author:oldminer

Many of you might not realize that the GIA clarity system makes subjective adjustments for the amount of inclusions and blemishes depending on the size of the diamond. As stones increase in size, the grading may appear to liberalize. Diamonds of 4 carat might have visible inclusions that would be graded I1 in a carat size stone, yet only grade SI1 in a 4 carat stone.

But why, the inclusions are either visible or they aren’t... This does not follow their little own definitions.

but... it does make sense.do you really expect to see a 5 ct SI1 stone with the same size inclusion as a 1 ct SI1?

yes, because that is how they are defined on the GIA website.
How hard they are to see under 10x.
Anything else is not right.

 

[strmrdr]

From:
http://www.gia.edu/mothersday2004/26695/clarity.cfm

Dare I say the fr--- word?


GIA Clarity Scale

(FL) FLAWLESS
Shows no inclusions or blemishes of any sort under 10X magnification when observed by an experienced grader.

(IF) INTERNALLY FLAWLESS
Has no inclusions when examined by an experienced grader using 10X magnification, but will have some minor blemishes.

(VVS1 and VVS2) VERY VERY SLIGHTLY INCLUDED
Contains minute inclusions that are difficult even for experienced graders to see under 10X magnification.

(VS1 and VS2) VERY SLIGHTLY INCLUDED
Contains minute inclusions such as small crystals, clouds, or feathers when observed with effort under 10X magnification.

(SI1 and SI2) SLIGHTLY INCLUDED
Contains inclusions (clouds, included crystals, knots, cavities, and feathers) that are noticeable to an experienced grader under 10X magnification.

(I1, I2, I3) INCLUDED
Contains inclusions (possibly large feathers or large included crystals) that are obvious under 10X magnification and may affect transparency and brilliance.

 

[oldminer]

Strmrdr:

All of those definitions are great, but they simply failed to say that this is what they teach and it applies to diamonds of 1/2 carat or less. Diamonds of larger weight / size are graded on a sliding scale that the GIA TL uses, but does not share readily with us peons.


Jeff:

By consensus, I mean a representative majority of knowledgeable gemologists and scientists who agree that a certain, relatively objective set of grading standards is workable, meaningful, teachable, accurate and repeatable. This situation may arise as technology iand education ncreasingly makes us aware of current shortcomings in the system we now use. The present system has worked satisfactorily for many years, but it is far from perfect. Making it more sensible would be a first priority.

 

[Dancing Fire]

strmrdr
i know what you''re saying but,it ain''t gonna happen.if what you saying is true then,we can all go out and buy a 10 ct "eye clean" SI1 and don''t even need to look at the VVS stones.

 

[wayne@gemex]

Date: 4/6/2006 10:52:19 AM
Author: klavigne
So Dave,

It would seem that what you are telling us is that inclusions are graded based on the percentage size of said inclusions? So with a larger diamond you really need to be in the higher range to have an eye clean stone? So a 5 carat VVS1 could possible have the same ''percentage'' of inclusions as a 1carat SI1? Or said differently, if the 5 carat stone has a 5 micron inclusion and the 1 carat had a 1 mircon inclusion, they wouldn''t be graded the same? Is that the jist of this? I guess it all really does make sense if stated this way.

Hi Klavigne

There is a lot more to clarity grading than just the size of the inclusion. Other factors considered are the position of the inclusion in the stone and the contrast of the inclusion. These factors all influence the visibility of the inclusion and therefore the final grading. For example, a 100 micron inclusion under the table in a 1/2 carat stone will be significantly more visible than a 100 micron inclsion under one of the crown facets in a 1 carat stone and the grading will reflect these accordingly.

The point is that a clarity grading is not simply a reflection of relative size of the inclusion to the size of the diamond and many other factors are considered.

 

[strmrdr]

Date: 4/6/2006 7:57:21 PM
Author: Dancing Fire
strmrdr

i know what you''re saying but,it ain''t gonna happen.if what you saying is true then,we can all go out and buy a 10 ct ''eye clean'' SI1 and don''t even need to look at the VVS stones.

yes and thats the way it should be.
If si1 is eyeclean at 1 ct it should be at 10ct or 20ct.
Now if you wanted to argue that the 10ct should be allowed more small inclusions then yes I could go along with that but not bigger inclusions.
ie: take 5 small inclusions that make a diamond a vs2 at 1ct and spread the same 5 inclusions over a 20 ct I could see it being a vs1.
But to take a huge eye visible feather in a 20ct and call it vs2 is wrong.

 

[DiamondExpert]

Dave - do you know if there are some large stones having 10x-visible pinpoints which are graded IF, or is there more consistency at the top end of the clarity range?

 

[Garry H (Cut Nut)]

Great topic Dave.

If we are going to look at fundementals - then surely the biggest mistake of the previous century is to grade diamonds with back lighting?

In the real world we see inclusions with light that comes from above the girdle!

 

[oldminer]

IF never has eye visible pinpoints. At the very top end, the rules are stringent.

 

[klavigne]

Wow, I don''t think I trust any of these labs anymore. So where is the cutoff for allowing certian sizes to pass at higher grades then? Is it right at the half carat range like you mentioned? If thats the case then any stone over .5ct is probable graded wrong? So if we can''t trust the labs to be consistent with something as "simple" as one of the 4C''s how can we trust tehm with anything else? You guys need to get together and start your own lab!!!!!! I''ll start looking for grant monies

 

[Richard Sherwood]

I think the labs are doing a good job of clarity grading larger stones.

It''s really simple, if you think of it in terms of relativity. The GIA standards work best in the 1/2 carat to 1 carat range. Anything smaller than that, you grade in perspective to the size, and anything larger than that, you grade in perspective to the size.

Let''s say you''ve got a 1 carat with a certain size inclusion, SI1 for example. If you shrunk that stone down to 10 points, of course the inclusion is going to be much smaller. Do you give it a VS1 then?

No. You grade taking into account the relative size of inclusion to stone.

Let''s say you take that same stone and "grow" it to a 10 carat. Do you now give it a I1 because you can slightly see the inclusion? No, you grade it in perspective of the relative size of inclusion versus host stone.

It''s really not that complicated. It just requires training, experience and an expert opinion. That''s why you pay a respected lab to grade your stones instead of any Joe off the street with a loupe.

No need to trash the system. It works, and makes sense.

 

[RockDoc]

GIA changed the clarity grading significantly about 15 years ago.

Pressure from the diamond industry caused them to do this. Larger stones ( over 1.50carats) with smaller inclusions were being graded in the SI range, that now get VS grades

Basically the changes especially for larger stones, made logical sense to "loosen" the tolerances but these adjustments affected MOSTLY the diamonds in the VS- SI ranges.

IF, VVS are still very stringent.

There are some SI-2''s now that might have been I-1''s in previous years.

The biggest problem I see, is that some of the labs use the same terminology of grading ( VS, SI etc.) but the don''t follow the GIA standards, which can be very confusing to the buying public.

For me, even the published definitions of GIA clarity grades is not uniform to the way the lab grades, but as Dave and Richard have pointed out, understanding and judging how a clarity grade is actually determined, can be a lot more complex to understand, and not really understood by consumers.

Many of the diamond selling website, attribute a stone''s being eye clean... GIA''s system does not address this factor, although lots of consumers believe it does, as many websites state that certain clarity grades are or aren''t eye visible, and this is not factual.

Rockdoc