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GIA vs. IGI


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#1 Bobtheelf

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Posted 12 December 2006 - 09:11 AM

Hi everyone,

Is the difference between GIA and IGI truly as great as I've heard? Can I expect basically a one grade change on each catagory, so that an H with IGI would probably be an I with GIA, etc?

-BTE

#2 diamondsonfifth.com

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Posted 12 December 2006 - 10:11 AM

Sometimes even two grades lower

#3 diamondsbylauren

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Posted 12 December 2006 - 01:13 PM

Hi Bob,
There's really no comparison at all between GIA and ANY of the other labs.


The problem is far greater than the simple misgrading that does occur.
The main problem is that dleaers know they can't get legitimate pricing on diamonds without GIA reports.
This leads to a few situations:
1) Sellers trying to convince buyers that their H/Si1 ( with a substandard report) is the same as a legimately graded diamond.
In this case it's a question of honesty. Any major dealer knows all this stuff.
2 ) Based on the market, ANY major diamond worth it's salt is going to GIA.
The lesser cut, less attractive stones go to the lesser labs.
SO- A diamond shopper looking at non GIA reports is going to see the least desirable diamonds- hopefully from a dealer honest enough to let the buyers understand this. But we all know a lot of dealers are using the lack of knowledge to attempt to decieve the buyers.

#4 Bobtheelf

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Posted 12 December 2006 - 06:57 PM

Hi Bob,
There's really no comparison at all between GIA and ANY of the other labs.


The problem is far greater than the simple misgrading that does occur.
The main problem is that dleaers know they can't get legitimate pricing on diamonds without GIA reports.
This leads to a few situations:
1) Sellers trying to convince buyers that their H/Si1 ( with a substandard report) is the same as a legimately graded diamond.
In this case it's a question of honesty. Any major dealer knows all this stuff.
2 ) Based on the market, ANY major diamond worth it's salt is going to GIA.
The lesser cut, less attractive stones go to the lesser labs.
SO- A diamond shopper looking at non GIA reports is going to see the least desirable diamonds- hopefully from a dealer honest enough to let the buyers understand this. But we all know a lot of dealers are using the lack of knowledge to attempt to decieve the buyers.


David - Thanks for the reply. Does this hold true for AGS as well?

#5 diamondsbylauren

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Posted 13 December 2006 - 11:38 AM

Hi Bob,
I should have mentioned the AGS is also accepted on par with GIA.
BUT- since GIA has introduced a 'Cut Grade" it's made AGS far less important in the general scheme of things........

#6 the other jake

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Posted 14 December 2006 - 05:53 PM

Hi Bob,
I should have mentioned the AGS is also accepted on par with GIA.
BUT- since GIA has introduced a 'Cut Grade" it's made AGS far less important in the general scheme of things........



The AGS has a far superior cut measuring system. The new AGS System takes into account the following factors: an observer, a close viewing distance, appearance as distance varies, brilliance, fire, leakage, scintillation, 'spread', tilt, obscuration, girdle thickness, length-to-width ratio, polish, symmetry, durability and taste.

Using the current AGS system for comparison, GIA’s top grade is vast: A diamond graded GIA Excellent may be an AGS4 as easily as an AGS0. With GIA’s steep/deep allowances each lower AGS grade leads to extra weight within the same GIA grade. It is logical to presume that mass manufacturers will cut the heaviest possible GIA Excellent. Therefore, when a consumer is buying a GIA Excellent the statistical chance of him buying an AGS4 will be high. GIA may tell you that within their top grade there is no visible difference but AGS will tell you it can be divided into 5 different grades: It is impossible for both of these organizations to be correct. A vast top grade with abundant steep/deep combinations promotes sloppier cutting, which serves mass manufacturers, not the public.

Forced rounding: GIA reports altered measurements on their public grading reports. The current popularity of AGS documents and Sarin-type reports has developed a growing expectation among consumers for numbers reported to the tenth of a degree. GIA rounds numbers as much as 2.5 tenths and to nearest 5%. This is not accurate reporting.

Diamonds can be sent to any lab for grading and there is always a logical reason behind why it was sent to a particular lab: Diamonds receiving the AGS Ideal grade were sent there because the manufacturer was confident it would receive the pedigree. That is one reason they are rare; most diamonds in the mainstream would not qualify for an ideal cut grade, so why send them to AGS labs when another lab will give the stone better (or no) marks for cut?

Many diamonds of top beauty are sent to GIA because that lab has the largest global reputation for high quality. However, a diamond of nice color and clarity might also be sent to GIA because the maker knows it would not receive top marks in cut from AGS.

#7 diamondsbylauren

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Posted 14 December 2006 - 06:40 PM

Hi Jake, I suppose we all have our own perspective- and our own taste in what is beautiful.
That's where GIA's cut grade has AGS's trumped.
I've always felt that a really well cut 60/60 was the best looking ruond diamond- and a lot of cutters agree.
No question, an "Ideal Cut" by AGS old standards, can be a beautiful diamond, but I don't see it as "better" than 60/60.
Neither did GIA, who's "EX' Cut Grade includes diamonds of 60% depth and 60% table- providing all the other factors are correct.
GIA's Cut Grade is based on visual observation- on addition to all the factors you metnioned.

GIA's EX Cut Grade sells at a premium,
I have heard theat AGS diamonds are a bit softer in the market this year, and I'm not surpirsed.

#8 denverappraiser

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Posted 15 December 2006 - 05:24 AM

There are GIA-excellent's that don't score an AGS-0 and there are AGS-0's that don’t score a GIA-excellent. They simply aren't looking at the same things. AGS is terribly specific about what they consider to be optimum but beauty is a difficult and moving target to try to optimize. Both labs are including commercial realities into their scales that could be described as ‘catering to manufacturers' so I don't think it's fair to be laying that strictly on GIA.

In Tolkowski's original treatise, Diamond Design, which is the basis of the AGS grading approach, his optimum diamond had a 53% table and a knife edged girdle. Both are currently unpopular attributes that would force a stone to be sold at a discount. Was he wrong, or have tastes simply changed since that was written in 1919?

The entire text of Diamond design is here for those who want to dive down the rabbit hole. It reads a little like a math book but it's only 130 pages long and it's really very interesting for those who are into this stuff: http://www.folds.net...mond/index.html

I'm inclined to agree, I like the AGS system better both because it's more specific and the whole process is more transparent but I also agree with David that there are some rip snorting lovely 'excellent' cuts that will knock her socks off and that don't meet the AGS specs for idealness. 'Ideal' does not mean 'best', nor does AGS claim it does.

I also agree that AGS lab is a considerably easier company to do business with and that they are much more forthcoming with data but they also carefully select what does, and what does not, go onto a report that's being released to the public. In neither case is sufficient information provided on the report to independently verify their cut grading conclusions using nothing other than data that they have provided.

I consider information about a stone from AGS Lab to be at least as reliable for shoppers as information from GIA and, in some cases better.

Neil
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#9 diamondsbylauren

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Posted 15 December 2006 - 01:15 PM

Interesting Neil!
Just curious.....If you drew the "perfect"- or your favorite- round diamond, in your mind's eye- would it have a "ideal" style cut, with the smaller table, or a 60/60 type of table?
What's your personal fave?

#10 denverappraiser

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Posted 15 December 2006 - 02:20 PM

David,

I have no taste. I'm an appraiser! :blink:

Neil
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#11 WebGal

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Posted 15 December 2006 - 06:19 PM

Okay, we'll keep it a top secret and not tell anyone. Go ahead, 'fess up your secret is safe here on the internet.
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#12 JohnQuixote

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Posted 16 December 2006 - 03:43 PM

Hi everyone,

Is the difference between GIA and IGI truly as great as I've heard? Can I expect basically a one grade change on each catagory, so that an H with IGI would probably be an I with GIA, etc?

-BTE


Yes. In general, there are significant differences.

Sure you are buying a diamond, not the paper… But also remember that the diamond was sent to one lab or the other for a reason: The best diamonds are sent to the GIA. Diamonds fitting the top cut paradigms of the AGS can be sent there because some people value that pedigree.

As an internet seller we swear by GIA and AGS standards. We send all diamond we have cut to those two labs exclusively. If asked, we recommend those labs exclusively. They have earned it.

Of course, most sellers of IGI-graded diamonds won’t volunteer that IGI's standards are softer. The key is learning the differences. If you ask objective people - like most professional appraisers - you'll find that what's being said here about GIA and AGS is true.

With that said...I’ve seen people who do learn the differences decide to go ahead and buy a commercially cut, questionably-performing big old diamond graded by Joe’s Crab Shack anyway...in order to get the most bang for the buck. ;)

The most important element is becoming educated. Once a consumer has a reasonable overview of the big picture he can choose the path that suits him best.
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#13 JohnQuixote

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Posted 16 December 2006 - 04:06 PM

...I like the AGS system better both because it's more specific and the whole process is more transparent but I also agree with David that there are some rip snorting lovely 'excellent' cuts that will knock her socks off and that don't meet the AGS specs for idealness. 'Ideal' does not mean 'best', nor does AGS claim it does...

Neil


Right on.

AGS understands that the service they provide is more boutique. GIA understands that theirs is more global. The two organizations have the same roots and routinely support each other.

AGS is certainly more specific in what they’re looking for. That does not make them ‘right,’ but it does provide a service for those who value the narrow paradigms they have embraced. Frankly, those are some pretty stiff paradigms: AGS won’t give an ‘ideal’ cut grade to a diamond unless its polish and symmetry are both ‘ideal’ even though differences in VG and above are not visible. So, when you buy an ‘ideal’ cut grade you’re paying for finish workmanship you aren’t necessarily seeing.

GIA is trying to serve the planet. Everything The Other Jake said is valid (and familiar). The other side of the coin is that GIA’s vast constituency is not best served by narrow parameters. GIA caters to a wider array in taste. To continue serving as the global standard bearer in as many markets as they’re invested, a wider cut grade is logical. Is the GIA system wider than AGS? Yes. Do some diamonds at the deep end of EX appear smaller for their weight than we would recommend? Yes. There are some issues, and we inform clients of such things in the same spirit we educate about AGS ‘ideal’ finish grades being more strict than they are visible.

Both of these labs have earned their place at the top.

David’s tastes are absolutely valid. So are Neil's secret-ninja tastes. So are mine. So are those of the next guy who walks into our offices. What will those be? The best service we can provide is to educate consumers about all of the options and let them choose.
John Pollard

#14 barry

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Posted 16 December 2006 - 05:38 PM

GIA and AGS are the best grading labs extant.

Keep in mind, that an AGS Ideal or GIA Excellent does not necessarily guarantee a top-shelf visual performance diamond.

This is especially true of the AGS Ideal Princess Cuts.

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#15 laura87

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Posted 28 March 2011 - 11:33 AM

My understanding is that GIA has the strictest grading standards and the most accurate reports. I don't think I would be comfortable buying a diamond that was not GIA-certified. They have the best reputation in the industry and they developed the 4 C's in the first place.

#16 LaurieH

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Posted 28 March 2011 - 08:07 PM

Interesting old thread to pull back up. Made for a good read...
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