EGL vs. GIA with Data Comparison

[denverappraiser]

Hi Anne,

I think you have some very interesting data here. In my opinion the best way to find out what you are looking for is to run a regression analysis. Are you familiar with this methodology? If so I think the best way would be to gather as many similarly graded diamonds and using price as the dependent variable, make sure you have independent variables for all of the important value factors, including Gem Lab. By doing this you should get, within a certain tolerance, the price difference between the labs.

Good luck,

Tom,

I beg to differ unless the ‘tolerance’ you’re describing is so large as to make the results useless. If the raw data, meaning the weight/color/clarity information, isn’t consistent within a particular lab then you are making a terrible statistical mistake. What does the ‘average’ EGL-SI1 grade out at GIA? That’s the key topic and it’s the subject of the 17 stone study done by Pricescope a few years ago but, my opinion is that the results are misleading.

The average running speed of Steven Hawking and Florence Joyner is what it is and it isn't all that fast but without knowing more about both individuals, this statistic is meaningless. Parsing it to observe that all of the women in this group are significantly faster than average would be correct but equally meaningless, even if you toss in a dozen or so ‘normal’ people to make a bigger sample size.

The strategy of statistically ‘discounting’ various labs in the hope of finding a bargain is almost guaranteed to fail as a consumer, and usually as a dealer. It’s not that EGL doesn’t do good work or that they don’t produce reports with the same grades that GIA would give but, when they do, those stones either aren’t sold at the steep discount and/or they are resubmitted to a different lab for a pedigree that can be sold at a premium. Saying that comparatively expensive EGL’s are better, or at least closer to GIA grading than the less expensive ones ignores a whole issue about dealer behavior that trumps nearly everything so price isn’t really a very good indicator. What does that leave? Independent experts like you and me can certainly come into play, as can dealers who do their own in-house grading and sort the wheat from the chaff and consumers who are prepared to look at stones and apply their own grading expertise can make out but how is someone doing a statistical regression of the PS database going to do it? The average EGL graded stone is usually cheaper than the average stone from GIA with similar sounding specs. True, but so what? Statistics on how much cheaper is just a distraction.

 

[Doc_1]

Hi Anne,

I think you have some very interesting data here. In my opinion the best way to find out what you are looking for is to run a regression analysis. Are you familiar with this methodology? If so I think the best way would be to gather as many similarly graded diamonds and using price as the dependent variable, make sure you have independent variables for all of the important value factors, including Gem Lab. By doing this you should get, within a certain tolerance, the price difference between the labs.

Good luck,

Tom,

I beg to differ unless the ‘tolerance’ you’re describing is so large as to make the results useless. If the raw data, meaning the weight/color/clarity information, isn’t consistent within a particular lab then you are making a terrible statistical mistake. What does the ‘average’ EGL-SI1 grade out at GIA? That’s the key topic and it’s the subject of the 17 stone study done by Pricescope a few years ago but, my opinion is that the results are misleading.

The average running speed of Steven Hawking and Florence Joyner is what it is and it isn't all that fast but without knowing more about both individuals, this statistic is meaningless. Parsing it to observe that all of the women in this group are significantly faster than average would be correct but equally meaningless, even if you toss in a dozen or so ‘normal’ people to make a bigger sample size.

The strategy of statistically ‘discounting’ various labs in the hope of finding a bargain is almost guaranteed to fail as a consumer, and usually as a dealer. It’s not that EGL doesn’t do good work or that they don’t produce reports with the same grades that GIA would give but, when they do, those stones either aren’t sold at the steep discount and/or they are resubmitted to a different lab for a pedigree that can be sold at a premium. Saying that comparatively expensive EGL’s are better, or at least closer to GIA grading than the less expensive ones ignores a whole issue about dealer behavior that trumps nearly everything so price isn’t really a very good indicator. What does that leave? Independent experts like you and me can certainly come into play, as can dealers who do their own in-house grading and sort the wheat from the chaff and consumers who are prepared to look at stones and apply their own grading expertise can make out but how is someone doing a statistical regression of the PS database going to do it? The average EGL graded stone is usually cheaper than the average stone from GIA with similar sounding specs. True, but so what? Statistics on how much cheaper is just a distraction.

It sounds like the industry is air tight, and the price is set in advance from the early stages not leaving much room for the deal of the century.

 

[Tom Gelb]

HI,

Denver appraiser, you are absolutely correct, and I think that I misunderstood what the original poster was going for. The regression I was postulating would show how much an EGL cert is discounted from a GIA one. I am unsure what this would exactly mean, but it would not say anything about the relative merits of those labs, only the trade's perception of such. I certainly have my own, albeit biased, opinion about the labs, but this is not the place. And your point about using experts is well taken. As are the pitfalls of statistics and regression. As my professor said regression shows correlation and not necessarily causality, I only wish those who do medical studies would have the same disclaimer.

Thanks,

 

[AnneinGA]

All,
I am not looking for a way to prove that you can get a "needle in the haystack" EGL stone through math, regression, or any other data analysis. I was attempting to quantify the differences between certificate origin, price, grading, color and clarity.

The only way to specifically quantify the differences is to compare actual stones, send them to all three labs and compare the results, which has already been done, Charmy posted the link, and I read that with great interest because it was the actual detail of where I was trying to go.

The bottom line is a group of statements that I have formulated in my head about this entire process. For me they are "my truths" and what I am using during my search:

1. If I see an AGS cert, there is a really really good chance that it's a pretty diamond. There are pretty GIA diamonds too, but if someone paid to send the stone to AGS, they thought it was really worth doing. Crappy stones don't get an AGS cert. Most AGS diamonds score well on an HCA. A diamond with this reputation and this cert will cost me more money, but if I knew someone who wanted a good diamond and didn't want to learn a lot about a lot of things, I would make sure I told them to get a diamond with an AGS cert.

2. There are beautiful GIA diamonds, but there are also ones that don't have the light performance that they should. A GIA cert does not a pretty diamond make, necessarily. I have to be a little more discerning with a GIA stone because there are some really good ones and some really not so good ones.

3. Some EGL stones are beautiful and those who have purchased them feel that they got a great deal. The reason that stones are sent to EGL is because whoever is in charge of sending stones out has a reason for not sending them to GIA/AGS. Though the reason may not seem apparent to the buyer because the stone LOOKS or PERFORMS a certain way, there is a reason.

4. Looking at all the PS diamonds with GIA next to EGL and AGS makes me crazy. I found I could not -help- but try to compare them and thought to myself "but the EGL's are so much cheaper, I can get more for my money." That's like searching for four-door sedans and comparing a toyta to a lexus to a ferrari. In the end, I now do advance searches and only check AGS and GIA stones. Then I do not have the stone angst I had before.

4. I won't wear a certificate I will wear a diamond in a setting. Get what makes me happy.

5. Grading is subjective and comparing stones on paper is very difficult. In the end, I'll trust the cert, the inclusion map, the grading, the ASET, the Ideal Scope, the Sarin, and most importantly, my eye.

Still doesn't mean that I'm not interested in doing that regression stuff.

 

[Regular Guy]

3. Some EGL stones are beautiful and those who have purchased them feel that they got a great deal. The reason that stones are sent to EGL is because whoever is in charge of sending stones out has a reason for not sending them to GIA/AGS. Though the reason may not seem apparent to the buyer because the stone LOOKS or PERFORMS a certain way, there is a reason.

4. Looking at all the PS diamonds with GIA next to EGL and AGS makes me crazy. I found I could not -help- but try to compare them and thought to myself "but the EGL's are so much cheaper, I can get more for my money." That's like searching for four-door sedans and comparing a toyta to a lexus to a ferrari. In the end, I now do advance searches and only check AGS and GIA stones. Then I do not have the stone angst I had before.:

With these sorts of discussions...I find myself saying...he/she makes a good point (too).



Generally, where possible, I'd recommend not throwing out the baby with the bathwater.

Your friend who does not have answers, but who supports reasonable questions...

Ira Z.

 

[ChunkyCushionLover]

Anne,

The grading report's primary use is to determine a value in an objective manner using a repeatable set of measurements. This is far different from a subjective assessment of beauty made by a wearer, a dealer or any other evaluator which are much less repeatable and objective.

Person A may find an GIA L beautiful.
Person B may find an EGL J beautiful.

Person A and Person B may be looking at the same stone graded by two different labs, but this doesn't change the opinion of Person C who doesn't find either beautiful because it has too much warmth in their opinion.

The wholesale trade places a value on a gem's 4 Cs based on the GIA grading standard (the largest lab in NA), so using any other standard especially a less consistant one just distracts the buyer from a proper valuation. Color and Clarity are often considered rarity factors and are most important for value purposes, whereas cut is considered more of a beauty factor and has less of an impact on price.

First you need to determine your own standard by looking at diamonds, for Color, Clarity and Cut using a repeatable standard, then you need to search for the perfect stone using that same standard. Using a less consistant standard is just a distraction and may mean a consumer's preferences were a wider range than they were aware of.

 

[Doc_1]

Anne,

The grading report's primary use is to determine a value in an objective manner using a repeatable set of measurements. This is far different from a subjective assessment of beauty made by a wearer, a dealer or any other evaluator which are much less repeatable and objective.

Person A may find an GIA L beautiful.
Person B may find an EGL J beautiful.

Person A and Person B may be looking at the same stone graded by two different labs, but this doesn't change the opinion of Person C who doesn't find either beautiful because it has too much warmth in their opinion.

The wholesale trade places a value on a gem's 4 Cs based on the GIA grading standard (the largest lab in NA), so using any other standard especially a less consistant one just distracts the buyer from a proper valuation. Color and Clarity are often considered rarity factors and are most important for value purposes, whereas cut is considered more of a beauty factor and has less of an impact on price.

First you need to determine your own standard by looking at diamonds, for Color, Clarity and Cut using a repeatable standard, then you need to search for the perfect stone using that same standard. Using a less consistant standard is just a distraction and may mean a consumer's preferences were a wider range than they were aware of.

That is the reason for my question why there is no objective measurement of the yellow tint in the diamond.
what makes grader' A eye's more accurate than grader' B in seeing the yellow tint in a diamond and label it as such, and what makes grader A eye at the beginning of the day as accurate as the end of it, and what makes grader C representing people's average of perception of the yellow tint in the diamond.
other than the cut which is measured with accuracy, inclusions that are pinpointed and mapped, carat weight that is accurate too, the color measurement remains subjective and far from objective.

 

[ChunkyCushionLover]

the color measurement remains subjective and far from objective.

Doc_1,

I hope we are saying the same thing. Outside of a top tier lab like GIA or AGS the grading may be very subjective. From Gems & Gemology Winter 2008 referenced earlier in this thread:

Screening, Training, and Monitoring of GIA Color Graders.

Controlling all the conditions would be of little value without the proper screening and training of staff. At GIA, eligible staff members must pass tests such as the Dvorine Color Test, the Matchpoint Metameric Color Rule Test, and the Famsworth-Munsell 100 Hue Test to ensure that they have normal color vision, discrimination, and acuity. Other tests are designed to gauge visual and verbal understanding of the color grading process.

Training sessions with experienced graders allow those staff members who are accepted as new color graders to gain first-hand knowledge over a period of weeks. All staff members are routinely monitored through the data collection of "blind" observations on control stones as well, to help insure color grading consistency. To control for potential perception differences from individual to individual, GIA's grading process requires a minimum of two or three random, independent opinions (depending on the size of the stone). A consensus is required before a color grade is finalized. For larger or potentially D-color stones, the laboratory's computer operating system identifies
the need for the most experienced graders. Last, to avoid the potential of reduced accuracy due to eye fatigue, color grading sessions are limited to approximately one hour, at which point a minimum break of one hour must be taken.

 

[Doc_1]

the color measurement remains subjective and far from objective.

Doc_1,

I hope we are saying the same thing. Outside of a top tier lab like GIA or AGS the grading may be very subjective. From Gems & Gemology Winter 2008 referenced earlier in this thread:

Screening, Training, and Monitoring of GIA Color Graders.

Controlling all the conditions would be of little value without the proper screening and training of staff. At GIA, eligible staff members must pass tests such as the Dvorine Color Test, the Matchpoint Metameric Color Rule Test, and the Famsworth-Munsell 100 Hue Test to ensure that they have normal color vision, discrimination, and acuity. Other tests are designed to gauge visual and verbal understanding of the color grading process.

Training sessions with experienced graders allow those staff members who are accepted as new color graders to gain first-hand knowledge over a period of weeks. All staff members are routinely monitored through the data collection of "blind" observations on control stones as well, to help insure color grading consistency. To control for potential perception differences from individual to individual, GIA's grading process requires a minimum of two or three random, independent opinions (depending on the size of the stone). A consensus is required before a color grade is finalized. For larger or potentially D-color stones, the laboratory's computer operating system identifies
the need for the most experienced graders. Last, to avoid the potential of reduced accuracy due to eye fatigue, color grading sessions are limited to approximately one hour, at which point a minimum break of one hour must be taken.

I can go along and say yes that will minimize deviations from the average, but still subjective by all scientific standards,
Part of our training in internal medicine was how to dissect an article and a study, and the first rule of thumb is never to read the conclusion of an article without going through the process of criticizing the methodology. I was surprised how the same article can be seen in different ways.
Even if they have all those steps in place to choose and screen graders to keep the deviation minimal that is still subjective by all means.
A simple device that can measure optically the color in the diamond in not impossible to invent. I think the industry wants that part to be ambiguous to still have the premiums for the large steps of D/E/F......when the nitrogen inclusion in the diamond is more of a linear steps that could be measured optically.
The fact that the industry wants people to be in those large cutoffs is to keep the prices where the industry intend it to be.
If they came up with numerical measurement instead of the yellow tint J/F..., the prices may (am not sure) have more flexibility and be more fluid than the huge jumps from J to F ....etc!
That will give more chance to the consumer to let them judge with their own eye's perceiving the yellow tint in the diamond without being hit with those solid cutoffs of the colors now in place.
Does that make it better to consumer price wise or better to the industry i dunno, the fact that with all the advanced technology we have now they did not come up with such standard tells me the first is likely the case.

 

[ChunkyCushionLover]

Doc_1,

Read the article, understand the labs do have colorimeters already and inform yourself.
Perhaps you should study their methodology before you criticize it.

 

[Doc_1]

Doc_1,

Read the article, understand the labs do have colorimeters already and inform yourself.
Perhaps you should study their methodology before you criticize it.

As long as the deciding factor in the color grading and labeling is the grader's eye, that is still subjective.
I did not see the link to the article in your post, i was commenting on it, you rushed to judgment.
would you please post the link to the article and i will be happy to read it to inform my self more.

 

[AnneinGA]

I believe that GIA uses a set of master stones for color comparison and then compares the stone to be graded to the master set. So when they are grading a stone, they have a set standard to compare to. It's not just a diamond grader holding a diamond up and saying, "Oh, I thing that's a "G"." EGLUSA appears to use a grading process similary to GIA. This is probably why EGL USA stones fared better in the comparison study you posted earlier (see Grading a Diamond from EGLUSA):

"Grading a Diamond

Before a diamond gets the EGL USA "stamp of approval" and receives a certificate, it goes through the hands of at least eight professionals, four of which are trained gemologists. It takes a minimum of five graders just to grade the color and clarity of each diamond.

Color grading involves carefully comparing the ungraded diamond, under scientifically calibrated lighting conditions, to a special master set of diamonds with known color grades. The nuances between colors grades are very subtle, and color grading requires extremely accurate color vision. Two color graders plus a final grader must agree on the color of the diamond before the color grade is assigned. "

For this discussion, I think what would be helpful to know how EGL Int'l grades their stones. I looked on their website and looked on the web and didn't see NEAR the detail as GIA has. And then, who knows if EGL USA's stones are the same master stones as GIA.

Clarity is a whole other ballgame because no two stones are alike, I think it get's down to defining eye-clean, number of inclusions, etc. And hey, on a bad day with a hangover, people are human, and can miss one little inclusion.

 

[ChunkyCushionLover]

Doc_1,

Read the article, understand the labs do have colorimeters already and inform yourself.
Perhaps you should study their methodology before you criticize it.

As long as the deciding factor in the color grading and labeling is the grader's eye, that is still subjective.
I did not see the link to the article in your post, i was commenting on it, you rushed to judgment.
would you please post the link to the article and i will be happy to read it to inform my self more.

https://gia.metapress.com/content/20724977662v4236/resource-secured/?target=fulltext.pdf
Really Doc, claiming that every human color observation is subjective is trivial its a relative and repeatable observation.
Human grading has proven to be a more reliable indicator of human vision than the colorimeter GIA sells .

Here are the arguments(some no longer an issue) you could make criticizing GIA's methods all laid out for you nicely. http://www.ruby-sapphire.com/crying-game.htm None of them change the reality that GIA is as accurate and precise as any other source or lab and far better than most.

 

[Doc_1]

I believe that GIA uses a set of master stones for color comparison and then compares the stone to be graded to the master set. So when they are grading a stone, they have a set standard to compare to. It's not just a diamond grader holding a diamond up and saying, "Oh, I thing that's a "G"." EGLUSA appears to use a grading process similary to GIA. This is probably why EGL USA stones fared better in the comparison study you posted earlier (see Grading a Diamond from EGLUSA):

"Grading a Diamond

Before a diamond gets the EGL USA "stamp of approval" and receives a certificate, it goes through the hands of at least eight professionals, four of which are trained gemologists. It takes a minimum of five graders just to grade the color and clarity of each diamond.

Color grading involves carefully comparing the ungraded diamond, under scientifically calibrated lighting conditions, to a special master set of diamonds with known color grades. The nuances between colors grades are very subtle, and color grading requires extremely accurate color vision. Two color graders plus a final grader must agree on the color of the diamond before the color grade is assigned. "

For this discussion, I think what would be helpful to know how EGL Int'l grades their stones. I looked on their website and looked on the web and didn't see NEAR the detail as GIA has. And then, who knows if EGL USA's stones are the same master stones as GIA.

Clarity is a whole other ballgame because no two stones are alike, I think it get's down to defining eye-clean, number of inclusions, etc. And hey, on a bad day with a hangover, people are human, and can miss one little inclusion.

Thank you for the elaboration which goes to my side of the argument that now 2 C's out of the 4 are subjective!

 

[Doc_1]

Doc_1,

Read the article, understand the labs do have colorimeters already and inform yourself.
Perhaps you should study their methodology before you criticize it.

As long as the deciding factor in the color grading and labeling is the grader's eye, that is still subjective.
I did not see the link to the article in your post, i was commenting on it, you rushed to judgment.
would you please post the link to the article and i will be happy to read it to inform my self more.

https://gia.metapress.com/content/20724977662v4236/resource-secured/?target=fulltext.pdf
Really Doc, claiming that every human color observation is subjective is trivial its a relative and repeatable observation.
Human grading has proven to be a more reliable indicator of human vision than the colorimeter GIA sells .

Here are the arguments(some no longer an issue) you could make criticizing GIA's methods all laid out for you nicely. http://www.ruby-sapphire.com/crying-game.htm None of them change the reality that GIA is as accurate and precise as any other source or lab and far better than most.

CLL
Believe it or not the second article you linked to was on my book mark before and i did not fully read it. I was half through when you linked. and you can read in my previous post what was in line with the article about the hard stops in the grades that will make it subjective since an E can be joyfully D a year from now by another grader from the same lab or disastrously F.

 

[Doc_1]

The culprit is color meter being applied to the master set and still the subjective eye is comparing the diamond to the master set. you did not solve the subjectivity here at all.
the objective to apply the color meter and numerically measure the color in the diamond itself.
but that will remove the hard stops of the grading and the industry does not like that.

 

[AnneinGA]

Doc,

I don't think that two of four are subjective.
I think that Cut and Carat are obviously, definitely not.

Color, judged against master stones is a small percentage subjective, but since there is more than one eye on the stone, there has to be a consensus. One person doesn't say "it's a G" and then forever more it's a G. There is more than one eye on the stone.

Clarity has a greater margin for error, but even the individual grades are defined. Until computers judge stones (is this done yet?) This is the one place for a greater percentage of subjectivity, but it's not completely subjective, there are standards.

The graphic I posted below is from the EGL USA site. I am sure GIA has something similar.

 

[Doc_1]

Anne
We (as i see it) are looking at the same thing from different angles.
your instinct as an accountant to come up with the study is dead on. it is a strong logic i see and i expressed it in a different way.
what i mean by that:
With the subjectivity of the color, and to a lesser degree the clarity. There is a window of opportunity.
That window is to see what is the color metering of an F diamond graded by GIA, lets say it measured (again i do not know how the color meter works i will learn about it though but lets compare it to our gulucometer we use in diabetes) and say for the sake of argument it was 500.
Then you pick another stone from GIA graded F and you measure it and it is 510.
now if you pick a diamond from a different lab that is graded F and you measure it by the colormeter to find it read lets say 400.
then you have no incentive to buy that diamond since it will rate less on GIA. but if that different lab was an underdog and had lesser value for the same grade and that F measured 507 then there is a window of opportunity to benefit from the difference in the subjectivity between labs.
those numbers are not real but the idea is to measure the diamond itself with the color meter, if we base decisions of life and death for insulin doses on the color measurements of the blood glucose, heck diamonds are a whole a lot easier.
I am very respectful to your line of thought and i see a very sound logic in it. I hope there is a way to add to the numbers (since you love them as an accountant) the numerical value of the diamond's color itself, am not sure how feasible that will be i know the industry will oppose it tooth and nails since it will remove the hard stops and make it more linear which may in turn lessen the premiums on those jumps in grades.

 

[Tom Gelb]

This is an interesting discussion, but I think it is important to note that nitrogen is only one method of coloration of a "colorless" diamond. Also it is not the amount of nitrogen that determines the amount of tint, but the amount of nitrogen in certain aggregations. Some D color diamonds have a lot of nitrogen, but in an aggregation that causes no absorption of light. Colored crystals, Hydrogen, structural defects, Boron and natural radiation damage , or any combination thereof, can also give a slight (sometimes not so slight) tint to a diamond. And the method of testing for color must be non-destructive. Thus we are left with measuring absorption, which if you do not know the distance the light travels through the diamond (it may bounce a number of times before leaving the stone) cannot be done quantitatively (at least this is what I have been told). So the color measuring devices are not simple to make.

Just food for thought.

Good luck.

 

[Doc_1]

This is an interesting discussion, but I think it is important to note that nitrogen is only one method of coloration of a "colorless" diamond. Also it is not the amount of nitrogen that determines the amount of tint, but the amount of nitrogen in certain aggregations. Some D color diamonds have a lot of nitrogen, but in an aggregation that causes no absorption of light. Colored crystals, Hydrogen, structural defects, Boron and natural radiation damage , or any combination thereof, can also give a slight (sometimes not so slight) tint to a diamond. And the method of testing for color must be non-destructive. Thus we are left with measuring absorption, which if you do not know the distance the light travels through the diamond (it may bounce a number of times before leaving the stone) cannot be done quantitatively (at least this is what I have been told). So the color measuring devices are not simple to make.

Just food for thought.

Good luck.

the colormeter is used on the master set though, so you are relying on the colormeter to set the standard for the grade cutoffs, it is used on what you are measuring to, so you can easily use it with accuracy on the diamond itself.
if the color meter is used on the diamonds we may be shocked from the results of particular grade lab reports of the same lab.
the incentive to have an objective way of measuring the color of the diamond is simply not there, it is a conflict of interest.

 

[ChunkyCushionLover]

The culprit is color meter being applied to the master set and still the subjective eye is comparing the diamond to the master set. you did not solve the subjectivity here at all.
the objective to apply the color meter and numerically measure the color in the diamond itself.
but that will remove the hard stops of the grading and the industry does not like that.

Doc_1,

GIA Carlsbad lab does use a Colorimeter to grade stones. Since 2001 where they tested it on tens of thousands of stones and have validated it for grading color. It is currently integrated as an opinion in the GIA grading process with visual agreement by one or more graders required to finalize the color grade. Since then, the vast majority of diamonds passing through the laboratory have been graded by combining visual observation with instrumental color measurement.

 

[Regular Guy]

Ummm......

Earlier, I proposed not throwing out the baby with the bathwater.

Despite my having been here a really long time (over 6 years?), I wonder if you guys are simply talking about what year the bathtub was manufactured.

That is to say...yes...with respect to color, I read from Richard Sherwood and others that a device like the SAS2000 has really amazingly "spot on" performance, such that while a colorimeter may be less than perferred, other devices can point to the potential objectification of the color process. If...that is really the point...

Anne has been able to repeat what Denver/Neil has most critically commented on, allowing Anne to repeat the refrain....smart guys like diamond cutters send diamonds to labs strategically, and know what they are doing. So, what's the darn difference what the color of the diamond is with respect to choice of the lab. The critical decision criteria surely...if it is to be meaningfully understood in some kind of way, has something to do with a characteristic of the diamond outside of the universe we are even discussing here....otherwise...this is simply not very interesting.

And yet, I have never found anyone with credentials to speak about this "black box" of strategic choice. I can make inferences, but they are based on nothing...vapors.

Berryl I belive has mentioned a 5th criteria...the diamond material itself. That the nature of the diamond "matter" has variability, and perhaps this will have something to do with it.

I really don't know.

Otherwise, although we yes know that using 3rd & 4th tier grading agents will have implications for the shopper, apart from knowing that there is increasing unpredictability concerning what is actually known about those old 4 Cs....I am betting right about now that those 4 Cs do not make up the universe upon which such a supposed strategic choice is made. Otherwise, why is the statement about this so called "strategic" choice as provocative as it would seem to be...?

Ira Z.

 

[Doc_1]

The culprit is color meter being applied to the master set and still the subjective eye is comparing the diamond to the master set. you did not solve the subjectivity here at all.
the objective to apply the color meter and numerically measure the color in the diamond itself.
but that will remove the hard stops of the grading and the industry does not like that.

Doc_1,

GIA Carlsbad lab does use a Colorimeter to grade stones. Since 2001 where they tested it on tens of thousands of stones and have validated it for grading color. It is currently integrated as an opinion in the GIA grading process with visual agreement by one or more graders required to finalize the color grade. Since then, the vast majority of diamonds passing through the laboratory have been graded by combining visual observation with instrumental color measurement.

You are strengthening my view of the color grading as subjective.
The red bold quote from your post is not any different than asking a person to carry a weight of one pound to verify if it is really one pound, or asking a person to look at a ruler to verify if the inch marked on it is really one inch.
However i will go along with you and ask
what are the units the colormeter measures the diamonds color with?
and what in those units are the quantitative measurements of what GIA labels D/E/F respectively?

 

[AnneinGA]

Ira,
My point with the data was to try to explore some of the other posts on this board that if you actually downgraded an EGL diamond to it's GIA graded color, that the EGL stone might be more expensive than the GIA counterpart.

As this thread has worn on, I realized that it is impossible to actually illustrate that. The GG Appraiser and the broker I talked to both agreed that the average is 1.5-2 steps on color and clarity. However, without seeing the individual stones, it would be just as skewwed to assign these lower values to all EGL stones in the data set.

I still believe that of all the C's that Color and Clarity have the only percentages of subjectivity. I believe that with the tools in the business that the percentage of subjectivity used to assign color is lower than clarity. I'm not sure how we got off in the weeds of the color meter because truth be told there are just some parts of the process I have to accept as is, and how it's calibrated is not really my thing. It's the standard. All GIA stones are graded with the standard. It is what it is.

My own truths haven't changed. Interestingly enough a few weeks ago when Yenny and I met and went to the broker in Atlanta, we played "guess the color" with EGL stones. It was GREAT to see EGL against GIA stones; and Yenny and I mostly guessed right, what we thought the color should be, which was generally a step or two lower than the EGL grade. It was a very helpful exercise.

At this point even a regression analyis would have to make the same assumptions about the 1.5-2 steps so it would not be accurate. The best study on this was the one Charmy posted towards the top of the thread where actual stones were sent to all three labs. I know it's a small study but it was the most telling for me. Because again, I'm about the data.

Thanks for your thoughtful replies.

 

[Doc_1]

Ummm......

Earlier, I proposed not throwing out the baby with the bathwater.

Despite my having been here a really long time (over 6 years?), I wonder if you guys are simply talking about what year the bathtub was manufactured.

That is to say...yes...with respect to color, I read from Richard Sherwood and others that a device like the SAS2000 has really amazingly "spot on" performance, such that while a colorimeter may be less than perferred, other devices can point to the potential objectification of the color process. If...that is really the point...

Anne has been able to repeat what Denver/Neil has most critically commented on, allowing Anne to repeat the refrain....smart guys like diamond cutters send diamonds to labs strategically, and know what they are doing. So, what's the darn difference what the color of the diamond is with respect to choice of the lab. The critical decision criteria surely...if it is to be meaningfully understood in some kind of way, has something to do with a characteristic of the diamond outside of the universe we are even discussing here....otherwise...this is simply not very interesting.

And yet, I have never found anyone with credentials to speak about this "black box" of strategic choice. I can make inferences, but they are based on nothing...vapors.

Berryl I belive has mentioned a 5th criteria...the diamond material itself. That the nature of the diamond "matter" has variability, and perhaps this will have something to do with it.

I really don't know.

Otherwise, although we yes know that using 3rd & 4th tier grading agents will have implications for the shopper, apart from knowing that there is increasing unpredictability concerning what is actually known about those old 4 Cs....I am betting right about now that those 4 Cs do not make up the universe upon which such a supposed strategic choice is made. Otherwise, why is the statement about this so called "strategic" choice as provocative as it would seem to be...?

Ira Z.

That is the very reason a consumer needs to be armed with an independent objective measurement of the diamonds color. regardless what the GIA crap they throw at you you will be able to know what you are getting, once you get those instruments in a hand held devices a consumer can carry (like glucometers for diabetics) then i can tell to you it will not be a black box any more.
I think changes are coming to the way the industry is handling this whether they like it or not, slowly but surely, and that is a good idea for a prospective study that some one can conduct that will reveal interesting results!

 

[AnneinGA]

Doc,

the GIA crap they throw at you

Really? You've gotta be joking.

Shall we start sending patients to see their doctors with their own thermometers and blood pressure cuffs, as well as blood meters in case that someone in the lab doesn't read the results right or the machine isn't calibrated.

At some point you have to let go a little and trust the system to work.

 

[Doc_1]

Doc,

the GIA crap they throw at you

Really? You've gotta be joking.

Shall we start sending patients to see their doctors with their own thermometers and blood pressure cuffs, as well as blood meters in case that someone in the lab doesn't read the results right or the machine isn't calibrated.

At some point you have to let go a little and trust the system to work.

I see conflict of interest setting the hard stops at those D/E/F....instead of more linear quantification of the color that normally exists.
Yeah...sure

 

[anitabee]

here's what i don't understand...

i recently saw about 5 princess of hearts here (in vancouver) at the local big mall. they were also canadian diamonds. anyhoo, i fell completely in love with the biggest one - a 2.19 carat, i color for $19,999 cdn.

i've never seen anything like it in real life. it was the most magnificent, gorgeous, fireball of a stone.

when i asked about its grading report the woman showed my an egl canada (aka egl usa) cert. all 5 of these newly arrived and beautifully displayed diamonds that were front and center had egl usa's to them.

why on earth would that vendor or the company (princess of hearts corp?) not send them out to gia or ags? mind you, we have an egl usa site here in downtown vancouver so it's close but still?...

for a $20,000 stone, wouldn't you think it would've been shipped off to gia? and please understand that it was TRULY the most beautiful set of diamonds i've ever seen. i was able to see the hearts and arrows pattern with the viewer she made available to me. phenomenal.

 

[Doc_1]

here's what i don't understand...

i recently saw about 5 princess of hearts here (in vancouver) at the local big mall. they were also canadian diamonds. anyhoo, i fell completely in love with the biggest one - a 2.19 carat, i color for $19,999 cdn.

i've never seen anything like it in real life. it was the most magnificent, gorgeous, fireball of a stone.

when i asked about its grading report the woman showed my an egl canada (aka egl usa) cert. all 5 of these newly arrived and beautifully displayed diamonds that were front and center had egl usa's to them.

why on earth would that vendor or the company (princess of hearts corp?) not send them out to gia or ags? mind you, we have an egl usa site here in downtown vancouver so it's close but still?...

for a $20,000 stone, wouldn't you think it would've been shipped off to gia? and please understand that it was TRULY the most beautiful set of diamonds i've ever seen. i was able to see the hearts and arrows pattern with the viewer she made available to me. phenomenal.

Strategically sent!

 

[stone-cold11]

The brand name probably more than made up for the difference in selling price for the stone if it were to get a GIA report. EGL-USA is the least offending of the EGL lab, also the company might have a relationship with the lab, might be cheaper and has a faster turn around time than GIA?