GIA misgrading stones with strong fluor?

[adamasgem]

Date: 9/17/2007 7:18:39 AM
Author: oldminer
I also have an SAS2000 from Matry and it does exactly what Rich has indicated. I find it useful, but because it does grade differently than the GIA in the UV blocked mode, I rarely want to use it that way except to prove a point with someone about why lighting has an effect on color grading. For some reason(s) the SAS2000 does not grade all color like the GIA does. I think that as diamonds get larger, the grading system adjusts while the machine grades what is there on the device. An E color 6 carat diamond looks like an F/G color diamond because of absorption. The human eye and brain makes this adjustment where a device without programming to make this leap won''t.

Could it just be that GIA is appling "Certifigate" type adjustments to larger stones?

My intel is that GIA has been using their own "colorimeter" device on larger (5ct+) stones for awhile..

In my opinion, and the way I was taught, is that at the pavilion sweet spot, a 1ct E will look the same as a 5ct "E"

A 5ct "E" will have less nitrogen per unit volume than a 1ct "E"

Think of it as looking through multiple panes of glass, two panes of the same nitrogen concentration will be darker than one, in the absolute. If two panes have the same transmision as one pane, then they are the same color.

But don''t you have to look through the same "thickness" to compare color (or relative nitrogen concentration)?

If you are comparing color at the "same" equivilant relative pavilion position, then you are visually looking through greater thickness and a path length correction is in order (there is a "Size" button for that), and the path length for a RBC should be proportional to the diameter.

My baseline doesn''t look for a pathlength correction. I can walk you through the procedure.

 

[adamasgem]

Date: 9/17/2007 3:29:10 PM
Author: adamasgem

That goes to the issue, is it a ''new D'' or a ''True D'' and the age old standard that GIA once taught that ''diamonds should be graded in artificial light, devoid of ultraviolet''.

The correct GIA quote should be "Diamonds should be graded at their poorer color, in artificial light devoid of ultraviolet" as I remember.

 

[stebbo]

Date: 9/17/2007 10:29:48 AM
Author: Richard Sherwood
Yes, Stebbo & Angeline, you are understanding my statement correctly.

The GIA''s grading is usually in line with the SAS''s grading with the ultraviolet light filtered out, and then any improvement from color due to the fluorescent ''kick'' is above and beyond that, which also leads me to believe that the amount of UV in GIA''s grading lamps must be minimal.

Thanks for clearing that up Richard. Wonder why such a big deal is made of GIA non-filtered grading lights then...

 

[adamasgem]

Date: 9/18/2007 3:30:02 AM
Author: stebbo

Date: 9/17/2007 10:29:48 AM
Author: Richard Sherwood
Yes, Stebbo & Angeline, you are understanding my statement correctly.

The GIA''s grading is usually in line with the SAS''s grading with the ultraviolet light filtered out, and then any improvement from color due to the fluorescent ''kick'' is above and beyond that, which also leads me to believe that the amount of UV in GIA''s grading lamps must be minimal.

Thanks for clearing that up Richard. Wonder why such a big deal is made of GIA non-filtered grading lights then...

stebbo.. You will notice in Richards'' posts he says "most" or "usually" in line... now a VSB held right up to the light, like is shown on my web page from a GIA issued manual, can push the grade up by three grades better.

Even one color grade is a whole lot of money, especially on larger stones.

I guess your perspective can change if you are the seller or the end user. It is a big deal, because of the variability due to technique. If the lights were UV free or filtered, then technique wouldn''t matter.

 

[oldminer]

Marty is quoting what he says the GIA told him or has written in their literature. I think it is a little misleading in that they obviously do not follow this procedure or have modified it some time ago. I believe the key to GIA grading is to be a keen observer of what they appear to actually be doing in the lab do and make an expert attempt to mimic it when I grade. I don''t care if they use a little UV or none. It is a matter of consumers being comfortable their single diamond is fairly graded and fairly priced accordingly. Once a grader can mimic GIA results we have a fair situation which meets today''s rather archaic grading "standards". UV fluorescence has an effect on perceived color grade in some diamonds.

 

[oldminer]

Here are the images Rich Sherwood wanted to post. This is the indirect + daylight shot.

 

[oldminer]

Here is the indoor + fluorescent lighting image.

 

[oldminer]

This is the same diamond showing how strong the UV fluorescence is under direct black light.

 

[oldminer]

I adjusted the whiteness of the image done in indoor and fluorescent light. Now you can see that this stone is a little different in color than when in UV richer daylight You can also see that it does not have any visible cloudiness which is visible with UV rich lighting.
Even fluorescent lighting does have a UV component. Getting to the ACTUAL body color would be elusive is such as reactive stone. In daily wear one rarely finds themselves in a lighting atsmosphere without any UV.

 

[adamasgem]

Dave
Color grade a strong blue using a sheet of Lexan polycarbonate in and out between the light and the stone with your masters and you can visually see the shift relative to the non flurescent masters.

Also hold the tray closer to the light without the Lexan and you will also see the shift toward a more colorless (white)stone.

Yellow fluor stones will get worse in color.

This is one of the things I''d love to show a jury, with GIA being the defendant, and watch them squirm and try to double talk their way out of changing grading systems.

Better yet, I''d like to see them explain to some middle eastern prince why the 20ct "D" they bought is really an "F".
I hear they cut off the hands of thieves over there.

 

[oldminer]

I know you are right about what fluorescence may do to some diamonds when it comes to color grading. I also believe you have your facts straight as to what GIA says and teaches.

My concern is not with you, but with the complex reality of how the GIA Gem Trade Lab actually grades diamonds. We want students of our profession to know how to perform their job correctly. We want consumers to have places which they can trust. I teach grading skills and hope for students and employees to match GIA results, not parrot back rules which are not actually in use.

Rich's pictures above and the use of a Lexan filter are primary evidence that UV changes the perception of body color. How GIA chooses to grade these diamonds defers, to an extent, to the desires of dealers. Dealers want a document that people trust AND one which suits their desire to maximize profits. These things sometimes are not compatible goals, but the lab is in a pwer squeeze all the time to make these two goals attainable. Without real STANDARDS there is no hope of forcing more compliance. The rules are not objective in their present state.

 

[adamasgem]

Date: 9/18/2007 4:15:07 PM
Author: oldminer
I know you are right about what fluorescence may do to some diamonds when it comes to color grading. I also believe you have your facts straight as to what GIA says and teaches.
.

The issue Dave is how they have changed their teaching to pander to the trade, let alone what they said they practiced versus what they actually did in the lab.

I think that I have adequately documented their changing story over the years; and someone should do the arithmatic as to how much that cost the consumer. And they are a tax exempt institution, but then again we have the self perpetuating congress that is akin to GIA

 

[Richard Sherwood]

Thanks Dave. I like how you adjusted the whiteness to show a true comparison between the indoor/outdoor lighting photos.

Man, I love that indirect daylight shot.

It''s interesting also to see EGL-Antwerp''s opinion of "slight luminescence", eh?

 

[strmrdr]

Iv read this thread, Marty's page on it, and past threads and the question remains how big of an issue for most diamond shoppers is this really?

 

[adamasgem]

Date: 9/18/2007 6:11:44 PM
Author: strmrdr
Iv read this thread, Marty''s page on it, and past threads and the question remains how big of an issue for most diamond shoppers is this really?

One color grade on a borderline stone, can be thousands of dollars or more a carat, and with 25-30% of stones potentially influenced, that is how big an issue it is, Storm.

If you have read my article, you will see direct quotes of how a stone SHOULD be historically graded, from the horses mouth, GIA. Seems an interesting coincidence between when DeBeers went private and GIA changed their teaching. But they were leading up to it with their BS fluorescence article.

I was told in Vancouver once, that I should say that too loudly..

 

[strmrdr]

Date: 9/18/2007 6:47:05 PM
Author: adamasgem

Date: 9/18/2007 6:11:44 PM
Author: strmrdr
Iv read this thread, Marty''s page on it, and past threads and the question remains how big of an issue for most diamond shoppers is this really?

One color grade on a borderline stone, can be thousands of dollars or more a carat, and with 25-30% of stones potentially influenced, that is how big an issue it is, Storm.

Let me put this a different way.....
SB is discounted, the effect on MB and faint is more of an issue.
What is the effect? How big an issue is it on more typical stones?

 

[stebbo]

Date: 9/18/2007 6:47:05 PM
Author: adamasgem

Date: 9/18/2007 6:11:44 PM
Author: strmrdr
Iv read this thread, Marty's page on it, and past threads and the question remains how big of an issue for most diamond shoppers is this really?

One color grade on a borderline stone, can be thousands of dollars or more a carat, and with 25-30% of stones potentially influenced, that is how big an issue it is, Storm.

But you've agreed with Rich that 'usually' SB's are color graded correctly by the GIA, and SB is the amount of fluor that Rich observes is required to shift one color grade. Yet only around 4% of diamonds have strong or higher fluorescence - so doesn't that suggest that only something like 0.5 - 1% actually are affected?

 

[adamasgem]

Date: 9/18/2007 7:35:32 PM
Author: stebbo

Date: 9/18/2007 6:47:05 PM
Author: adamasgem

Date: 9/18/2007 6:11:44 PM
Author: strmrdr
Iv read this thread, Marty''s page on it, and past threads and the question remains how big of an issue for most diamond shoppers is this really?

One color grade on a borderline stone, can be thousands of dollars or more a carat, and with 25-30% of stones potentially influenced, that is how big an issue it is, Storm.

But you''ve agreed with Rich that ''usually'' SB''s are color graded correctly by the GIA, and SB is the amount of fluor that Rich observes is required to shift one color grade. Yet only around 4% of diamonds have strong or higher fluorescence - so doesn''t that suggest that only something like 0.5 - 1% actually are affected?

Stebbo.. I think your low percentages are very overly optomistic, espescially on larger stones...

Any fluor can effect the color grade, if done under UV environment. I didn''t necessarily agree with Rich, just stated "usually" and "most", but I dare say the numbers are significantly higher..

Althogh not keeping specific track, I''d say that at least 15% are overgraded in color, from my experiance.

Now if we look at European paper, the numbers are much much higher..

 

[adamasgem]

Date: 9/18/2007 7:13:40 PM
Author: strmrdr

Date: 9/18/2007 6:47:05 PM
Author: adamasgem

Date: 9/18/2007 6:11:44 PM
Author: strmrdr
Iv read this thread, Marty''s page on it, and past threads and the question remains how big of an issue for most diamond shoppers is this really?

One color grade on a borderline stone, can be thousands of dollars or more a carat, and with 25-30% of stones potentially influenced, that is how big an issue it is, Storm.

Let me put this a different way.....
SB is discounted, the effect on MB and faint is more of an issue.
What is the effect? How big an issue is it on more typical stones?

First of all Storm, the "Rap" discount on fluor is not necessarily equivilant to the price shift versus color grade...

If you call an average of $1K on 15% or more of "typical" stones not an issue, I''d suggest you do the math.
While the wholesale is discounted, the typical consumer doesn''t see the savings, it is all put into the pockets of the mall retailer as additional profit, and that is where

Now if you buy an IF, atypicaal, then on a 1ct stone, you are looking at $6K per carat wholesale between a "D" and an "E", not chump change at all.

 

[Garry H (Cut Nut)]

Date: 9/18/2007 4:15:07 PM
Author: oldminer
I know you are right about what fluorescence may do to some diamonds when it comes to color grading. I also believe you have your facts straight as to what GIA says and teaches.

My concern is not with you, but with the complex reality of how the GIA Gem Trade Lab actually grades diamonds. We want students of our profession to know how to perform their job correctly. We want consumers to have places which they can trust. I teach grading skills and hope for students and employees to match GIA results, not parrot back rules which are not actually in use.

Rich''s pictures above and the use of a Lexan filter are primary evidence that UV changes the perception of body color. How GIA chooses to grade these diamonds defers, to an extent, to the desires of dealers. Dealers want a document that people trust AND one which suits their desire to maximize profits. These things sometimes are not compatible goals, but the lab is in a pwer squeeze all the time to make these two goals attainable. Without real STANDARDS there is no hope of forcing more compliance. The rules are not objective in their present state.

well said Dave.
Repeatability is of course another issue.

I often ask myself about all sorts of issues - "what will it be like in 100 years?"
Where I live I expect to see skyscraping apartments and less tress and lawn.
I doubt much diamond grading will be done by low paid production line lab rats.

 

[Garry H (Cut Nut)]

I continue to believe high color strong and VS blue diamonds are a bargain.

I also welcome the day when all color grading is done face up.

 

[Richard Sherwood]

I love colorless stones with strong blue fluorescence. Always have. They used to be called "blue white" diamonds, and commanded a premium, back before visual presentation outweighed numbers and letters.

Some things have improved with the "quantification" of diamonds. Other things have not. Those who are able to tell the difference will always profit. Beauty always trumps numbers.

 

[stebbo]

Date: 9/18/2007 9:56:20 PM
Author: adamasgem

Date: 9/18/2007 7:35:32 PM

Author: stebbo


Yet only around 4% of diamonds have strong or higher fluorescence - so doesn't that suggest that only something like 0.5 - 1% actually are affected?

Stebbo.. I think your low percentages are very overly optomistic, espescially on larger stones...

I don't think so. Only 4% of James Allen's 20,000 listed stones are strongs or higher, as are only 3.9% of Blue Nile's 65,000. Of course, they're not statistics agencies but I think they reasonably represent what's out there.

3 out of 4 I think generously covers 'usually' or 'most'.

Larger stones, yeah, there's more, but it's still under 6% for 2 carats and bigger (sample size 8500). Despite such sizes being only 15% of the population, I do however appreciate the effect of misgraded color is amplified here.

 

[Garry H (Cut Nut)]

Question for the gathered gliterate''

We know that as size increases that the effect of a little color becomes greater.
We also know that as ray path gets longer (eg radiant) that face up color becomes more distinct.

Does fluoro play out the same way in both the above cases?

 

[adamasgem]

Date: 9/19/2007 12:29:28 AM
Author: stebbo

Date: 9/18/2007 9:56:20 PM
Author: adamasgem

Date: 9/18/2007 7:35:32 PM

Author: stebbo


Yet only around 4% of diamonds have strong or higher fluorescence - so doesn't that suggest that only something like 0.5 - 1% actually are affected?

Stebbo.. I think your low percentages are very overly optomistic, espescially on larger stones...

I don't think so. Only 4% of James Allen's 20,000 listed stones are strongs or higher, as are only 3.9% of Blue Nile's 65,000. Of course, they're not statistics agencies but I think they reasonably represent what's out there.

3 out of 4 I think generously covers 'usually' or 'most'.

Larger stones, yeah, there's more, but it's still under 6% for 2 carats and bigger (sample size 8500). Despite such sizes being only 15% of the population, I do however appreciate the effect of misgraded color is amplified here.

I think your statistics "statistics" my be misleading.. Try to find a 1/3 RBC that is VSB with a GIA dossier. Difficult. Been building a set for a potential court case to show a jury.

I graded some stones at a famous market makers booth in Vegas years back which had the typical mall store EGL Israel type paper, 3 to 4 color grades, D's with a cape lines as strong as a "J".

Do we "see" a lot of VSB's on the market, I think they are snapped up by the chains, like DI, the Jewelry Exchange, and the like before they get to the wholesale lists.

Nothing wrong with them if they are properly graded (unless they are overblues) and the consumer pays the appropriate 2 or 3 color grade discounted price and not the inflated color grade price. Who makes out? The mine owners and/or the sighhtholders.

And speaking of "D's". I did an availability study awhile back whicjh I posted on PS. Surprizing the distributional stats between labs on percentage of "D's" graded. How many very good "E's have you seen, fluor or not?

The data says something is real rotten, and thats because of the $$$$$ involved.

Most in the industry don't have a clue.

Ever wonder why GIA doesn't come after me regarding my overt stance on this issue, it is because they wouldn't stand a chance in court, period. I've documented their duplicity.

 

[strmrdr]

Date: 9/19/2007 2:00:07 AM
Author: adamasgem


Do we ''see'' a lot of VSB''s on the market, I think they are snapped up by the chains, like DI, the Jewelry Exchange, and the like before they get to the wholesale lists.

The GIA graded VSB and most of the SB''s rounds I have seen where at chain type stores.
When I saw GIA graded 1ct G VS stones advertised at slightly under PS price I went and checked them out and they were all vsb/sb and average cut which explained the price.

 

[Garry H (Cut Nut)]

Re the stuff sold at chains uncertified - every top light brown (TLB) that I have ever seen from Argyle - typically about K and a lot lower - is med to VS blue. Which is actually quite cool under the type of lighting chains are all using now - the low heat metal halides that are super white coldish. They throw out a heap of UV and the TLB''s look much less brown under them.

 

[diagem]

I have witnessed the GIA go from being lenient on fluo. high colored Diamonds back about two ago to being severely strict on the same type of goods in the last year or so.

I have seen GIA''s upgrading Fluo. high colored Diamonds back then. (for example H color with SB graded as G and even F''s)
And these days the GIA are down-grading Fluo. high colored Diamonds. (for example E-F''s with SB graded G and even H''s)


Something systematically happened in the last year or two switching up-grades to down-grades!!!

Could have been Marty''s spell?

 

[adamasgem]

Date: 9/19/2007 4:31:20 AM
Author: DiaGem
I have witnessed the GIA go from being lenient on fluo. high colored Diamonds back about two ago to being severely strict on the same type of goods in the last year or so.

I have seen GIA''s upgrading Fluo. high colored Diamonds back then. (for example H color with SB graded as G and even F''s)
And these days the GIA are down-grading Fluo. high colored Diamonds. (for example E-F''s with SB graded G and even H''s)


Something systematically happened in the last year or two switching up-grades to down-grades!!!

Could have been Marty''s spell?

Maybe they have found the error of their ways

They surely don''t want to confront me in a public forum, under oath

Double talking won''t work there..

As to E-F''s being G-H''s, maybe that is what they should be if they are SB.. SB''s can be two grades off easily, depends on how much UV is pumped in..
In the KittyDock(TM), the diffuser plat is not used in color grading, and it is not UV blocking..

 

[diagem]

Naturally, if you grade a MB to VSB colorless (D-G) Diamond in natural indirect northern daylight the Diamonds will stay colorless!
BUT!!! If you grade the same Diamond using "typical fluorescence" overhead Diamond office light (example: Philips F15T8/D), chance are some tint will show up.


So..., which is the correct way to grade???

, maybe face-up only like Garry is hoping??

I personally dont believe in face-up only grading