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. 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 fairly reliable laboratory.
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