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AGS Diamond Certification

The AGS (American Gem Society) prides itself on being the original lab to provide diamond cut grades.  Long before the GIA introduced their cut grade a few years ago, the AGS has been offering its unique cut grade scale from 0 to 9 (with 0 being termed “ideal”).

Back in those days, the AGS had the monopoly on the “ideal cut” market (with top vendors such as Brian Gavin Diamonds).  A diamond couldn’t be called “ideal” unless it has an AGS certificate claiming so.  Now that the GIA has entered the cut grade game, though, their market share in this market has dropped significantly.

Now, just as much people sell “triple X’s” (Polish, Symmetry, and Cut grades all receiving “Excellent” from the GIA) as they do “triple 0’s” (a “0” is the AGS equivalent of a GIA “Excellent”).


The AGS generally tries to bill itself as being a bit more fancy and refined than the GIA.  But the fact is there is hardly anything at all to distinguish the two except for the fact that the AGS is generally slightly looser than the GIA.

Most large diamond companies recognize this and take diamonds that don’t receive the intended grade and send them to AGS in order to receive an upgrade in clarity and color. Usually in those circumstances they succeed.

Unlike the EGL, however, there isn’t much of a market-wide consensus to this fact, so generally diamonds certified by the AGS sell at similar prices to their GIA equivalents.  If I had to suggest an average color and clarity upgrade from GIA, I would estimate a half a grade.

All in all, though, the AGS is a very reliable laboratory. At The Diamond Pro, we only recommend diamonds certified by GIA or AGS and we only work with vendors (such as James Allen or Brian Gavin Diamonds) that emphasize these two labs.

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Leave a Comment


  1. Julie     Reply

    Is this article correct? I’ve been told by six different geologists (went to a bunch speaking my perfect diamond) and they all voluntarily said that the AGS was more strict on cut compared to GIA even though they were all GIA certified gemologists.

    Their reason to me was because AGS has 0 for ideal and 1 excellent while GIA’s “excellent” is too broad a category and that the AGS platinum certificate for ideal diamonds is much kote expensive than a GIA certificate.

    So confused now because this article is the opposite of everything I’ve read and learnt from certified gemologists so far! Help!

    • Mike     Reply

      Hi Julie,

      Truth be told, its best that I re-work this article a bit. I’ll give you the basics here, but its a complicated question:

      AGS adheres to strict parameters of depth/table then determines the best angles to go along with them. GIA believes (and most people agree) that it isn’t that simple. There are times when a 59% table can be just as brilliant as a 56% table, so long as the entire diamond is proportioned correctly to maximize brilliance. They tend to use more of a sliding scale approach.

      So what does that mean for you? GIA has a much more nuanced approach that helps them determine brilliance more accurately. That said, they do tend to be a bit looser than AGS overall. In reality, I would not put one certificate over the other for brilliance.

      The one sure-fire advantage AGS offers is their light performance grade. Not all of their certificates offer it (its the red and green image), but that is useful. That is why you see that companies focusing on perfectly cut diamonds ( is our favorite of that bunch) stick with AGS certificates.

  2. Gobi     Reply

    I was sold the wrong diamond by a store in the USA. I had paid for a GIA certified SI1 with F clarity.

    But I just found out that the diamond is a 1.01 ct, SI2, G color with no Florescence and cut grade fair. The diamond is a round brilliant cut style. Polish and Symmetry is excellent. Table 55%, Depth – 67.3%, Girdle – slightly thick to extremely thick (faceted) 8%.

    Can you please guesstimate a price? I am not happy as I do feel cheated.

    • Mike     Reply

      Hi Gobi,

      I’m sorry to hear that. It is impossible to comment on the diamond without seeing it, but I can tell you the cut is way off as well.

      If you have a receipt that lists the diamond as an F SI1 GIA and proof that its a G SI2 GIA, you should contact a lawyer immediately.


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