AGS vs. GIA

[magnus]

I''m looking at a few different diamonds at GOG and was just curious about what the difference between AGS and GIA are. I''ve always thought that GIA was the certificate to get. Is AGS just as reputable?

 

[stone-cold11]

Yes. AGS is on par with GIA on color and clarity and considered better in terms of cut grading.

 

[arobert22]

Good old gold website has a very nice explanation of the different certs and will show you diamonds under ideal scope of GIA EX and AGS ideal. As you will see a GIA EX is in fact not always EX in terms of light performance but AGS ideal is

 

[Dreamer_D]

Some around these parts prefer AGS because they have a narrower criteria for ideal compared to GIA excellent cut grade. So there is a better chance for a super performer. But GOG also runs their own tests, and in their H&A lines all the GIA diamonds are winers (they do carry "traditional" diamonds that are not optically superideal, but it is easy to spot them).

 

[Lorelei]

Date: 12/17/2009 9:16:22 PM
Author:magnus
I'm looking at a few different diamonds at GOG and was just curious about what the difference between AGS and GIA are. I've always thought that GIA was the certificate to get. Is AGS just as reputable?

GIA and AGS are the two top tier labs and the gold standard of diamond grading. In fact, some prefer AGS's cut grading, this link explains how the grading labs rank

 

[dssxxxx]

I asked BN and here was their response, which I thought was clear and precise. This is a C&P.

For your information, as seen via the following link from our Web site, the below information serves to further elaborate on what differentiates GIA from AGS:
http://www.bluenile.com/diamonds/diamond-cut/diamond-cut-grading

Both GIA and AGS are equally as well respected and prestigious as the other as they both approach the science of diamond cut grade similarly.

GIA bases their new (as of Jan. 2006) cut grade on a combination of the following:
- Face-up appearance: Brightness, Fire, Scintillation
- Design: Weight Ratio, Durability
- Craftsmanship: Polish, Symmetry

Their belief is that these elements combined contribute to the diamond''s fire and brilliance.

GIA employs a predictive computer model, based on over 70,000 individual diamond observations and 38.5 million proportion sets, to determine a diamond''s brilliance based on its interrelated measurements. Most GIA diamonds graded prior to January 1st, 2006 will not have a laboratory-assigned cut grade. The GIA cut grade system includes ratings of Excellent, Very Good, Good, Fair and Poor.

GIA does not assign an Ideal cut and an Excellent rating is their highest grade. For comparison purposes, a GIA Excellent cut will be listed as a Blue Nile Ideal cut on our Web site. The cut grades are equivalent.

AGS determines cut grade using the following criteria:
- Light performance: Brightness, Dispersion, Leakage, Contrast
- Proportion: Girdle, Culet Size, Spread, Durability, Tilt
- Finish: Polish, Symmetry

AGS believes these characteristics best determine a diamond''s fire and brilliance.

When the AGSL determines a diamond''s cut grade, they look at a combination of 11 different criteria in these three categories, and then assign cut grades of Ideal, Excellent, Very Good, Good, Fair, and Poor. The AGSL labels a diamond that meets their standard of perfect proportions, polish, and symmetry as "Cut Grade: Ideal". An AGSL Ideal is known throughout the diamond industry as a "triple-zero" grade.

An AGSL Ideal cut is the equivalent of a GIA cut grade of Excellent or a Blue Nile Ideal cut. For comparison purposes, these cuts are all listed as Ideal on our Web site.

The following link is from the AGS Web site and provides further analysis with regards to the differences present amongst diamond grading labs:

http://agslab.com/matrix_consumer.php

I hope that this information is helpful.

 

[Regular Guy]

DSS,

This is helpful, but not clear enough.

To consider the 3 systems on par with each other is really just not accurate, nor reasonable.

You could consider venn diagrams, and sizes of hoola hoops, or whatever you like.

Someone will finesse this better then me, but simply put...

Given a total populations of reasonable diamonds to consider...

Where perhaps 2 - 15% would pass and get an AGS 0 grade for cut...

More clearly, 10 - 40% would get a GIA excellent grade, in comparison.

Get the idea. Some diamonds would get both.

Many more would be considered GIA excellent that would pass muster for AGS ideal.

Nevermind that there are also some differences in evaluation thrown in, to boot.