GIA vs. AGS vs. other

[dde]

1) I''ve been told that GIA certified diamonds are better than AGS. Primarily because AGS labs have been known to be off up to 2 grades. Is this true?
2) How can I tell if a certificate (GIA,AGS) is authentic? -

 

[Giangi]

Hiya and welcome!

I think AGS and GIA are at the same (high) level. The major problem I note in AGS reports is their lax grading of polish and symmetry. If a stone has ideal proportions, it's very easy that it gets a triple zero rating. Such high discrepancies are very unusual.
As for GIA... I have a problem with some of their SI 2. They are not as clean as they should be.

But they are both really excellent.

I still prefer HRD to GIA and AGS, though. The accuracy is very high.

Fake reports are pretty unusual, but you can tell them cause they do not always have security features as holograms and may not be laminated. Plus, you could call the lab and provide them the cert #... They will tell you if the cert exists.

 

[derekinla]

----------------
On 9/12/2003 2:58:51 PM Giangi wrote:

Hiya and welcome!

I think AGS and GIA are at the same (high) level. The major problem I note in AGS reports is their lax grading of polish and symmetry. If a stone has ideal proportions, it's very easy that it gets a triple zero rating. Such high discrepancies are very unusual.
As for GIA... I have a problem with some of their SI 2. They are not as clean as they should be.

But they are both really excellent.

I still prefer HRD to GIA and AGS, though. The accuracy is very high.

Fake reports are pretty unusual, but you can tell them cause they do not always have security features as holograms and may not be laminated. Plus, you could call the lab and provide them the cert #... They will tell you if the cert exists.

----------------

What is HRD? If an AGS stone gets a "0" for polish and a "0" for symmetry, how much variability is there in that grade. For example, could an AGS 0 score a "fair" "good" or "very good" on a GIA scale? Could one even begin to provide a rough ballpark correlation between the two grading systems for polish and symmetry into a table as follows:

Hypothetical Table:

GIA AGS

excellent 0 to 1
very good 0 to 3
good 3 to 7
fair 4 to 8
poor 9 to 10

 

[Giangi]

Hi derek!
HRD is Hoge Raad Voor Diamant. It is the standard in Europe and is far less recognised in the US.

There isn't a rule about discrepancies in GIA/AGS standards, but a GIA v.good/v.good very often gets AGS ideal/ideal.

 

[derekinla]

What do the gemologists on this forum think of this?

 

[dimonbob]

DDE
I don't know where you heard that GIA was better than AGS but that is a wrong statement. The man who runs the AGS lab is the same man that once ran the GIA lab in Los Angeles. The GIA grades diamonds the same as they graded them 35 years ago. AGS grades everything GIA grades plus grades the cut. It is possible that either lab has mis-graded a diamond now and then but to make a blanket statement that "AGS labs have been known to be off up to 2 grades" is not a fair or accurate statement.

Giangi
It is also not an accurate or fair statement to say that AGS reports are lax in grading of polish and symmetry. AGS grades polish the same as GIA so they are equal in that area. As far as symmetry goes AGS is far superior in that grading. You speak as though a diamond with a GIA ex ex and a Sarin report with AGS 0 would be equal or better than a diamond with just an AGS Ideal report. Not so. Most GIA ex ex with the right numbers would never make the grade as an Ideal because of the AGS strict grading of symmetry.
Of course there are a number of appraisers out there that think they are superior to either GIA or AGS and make a big noise about how they found a mis-graded diamond from one lab or another.
Please don't get me started on HRD. They also make mistakes!

 

[Richard Sherwood]

-----------
Of course there are a number of appraisers out there that think they
are superior to either GIA or AGS...
-----------

Out of the many appraisers I know, I don't know one who considers him or herself "superior" to GIA or AGS. I do know several, however, who do not consider themselves or their work "inferior" to that of the GIA or AGS.

 

[Richard Sherwood]

-----------
Giangi says- There isn't a rule about discrepancies in GIA/AGS
standards, but a GIA v.good/v.good very often gets AGS ideal/ideal.
-----------

Giangi, in the very few instances where I've seen an example of what you're saying here, it was because the GIA had failed to correctly grade the stone as excellent/excellent (or ideal/ideal in AGS terminology). To me, it doesn't so much seem that AGS is more liberal on their polish/symmetry grading, but rather that GIA sometimes doesn't give a stone it's full due in regards to these two characteristics.

----------
DimonBob says- As far as symmetry goes AGS is far superior in that
grading. You speak as though a diamond with a GIA ex ex and a Sarin
report with AGS 0 would be equal or better than a diamond with just
an AGS Ideal report. Not so. Most GIA ex ex with the right numbers
would never make the grade as an Ideal because of the AGS strict
grading of symmetry.
-----------

DimonBob, can you give some examples of how AGS is stricter in their grading of symmetry than GIA? I'm curious if this is your impression, or if you've seen it stated somewhere (perhaps in AGS literature)?

 

[DancinGirl]

"As for GIA... I have a problem with some of their SI 2. They are not as clean as they should be. "

Hi Giangi,

I personally don't think that is always the case. I have a GIA cert 1.07ct diamond that is an SI2, and even the person I bought it from said he was surprised it was graded an SI2 because it is very eye clean - and even under a loupe it hardly has as many flaws as a regular idea of an SI2. He even had to look twice at the Cert to make sure he read it right.

I have my own loupe and studied it more times than I can count here at home. I think it looks wonderful! I really only see one noticable tiny feather in mine and only through the loupe. I have seen other SI2 GIA certs with a lot more inclusions than mine has.

So - again, it doesn't happen in all cases. I think they (GIA) are maybe overly critical of a stone which is probably better sometimes rather than being too lienient.

Just my 2 cents...

 

[Giangi]

I stand corrected. I have a problem with SOME of their SI 2.
Not all are as clean as they should be. But some others are very nice to exceptional. Every stone should be evalued individually, but I think some SI 2's are a bit off. This is my opinion.

 

[DancinGirl]

That's okay - everyone is entitled to their own opinion, Giangi! THANKS!

 

[dimonbob]

Hi Richard - "DimonBob, can you give some examples of how AGS is stricter in their grading of symmetry than GIA? I'm curious if this is your impression, or if you've seen it stated somewhere (perhaps in AGS literature)?"

You forget that I was once a diamond grader at the GIA lab in Calif. Before I came to GIA I was trained about diamond cut by the guy who wrote the AGS Diamond Grading Standards. Does that make me an expert? No! But it helps.
Of course GIA-GTL haS made some slight changes since I was there but they still don't grade cut like AGS does. For one thing AGS grades each and every facet and facet junction. The facets should all point up, must not be misshapen, the crown and pavilion must be aligned. The difference between an AGS 0 and 1 is the 0 are Extremely difficult to locate under 10x and a 1 is very difficult to locate under 10x. GIA does not "study" the facets and facet junctions as hard.
Where do I get my information? Personal experience and knowledge plus talking with GIA & AGS people every year at Conclave.

 

[Richard Sherwood]

Thanks Bob.

 

[derekinla]

Very imformative,

Thanks Guys!!

 

[Dones]

What is the process to get a non-certified stone certified by AGI?

Help.

Dones