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AGS Also Changes Cut Scale

January 2005

While the GIA does all this, the AGS has also been busy, updating their round brilliant grade and announcing plans for cuts for square princess cuts. There are also plans for grades for other fancy shapes.

As with the GIA, the AGS system uses up-to-date technology, including three-dimensional imaging and optical ray tracing. It did not, like GIA, do extensive studies on human observations — which may be lower-tech but we suspect pretty useful.

The last time the AGS announced a major change in their cut grading (which became the current zero to ten scale) was 1990. While their old cut grade system was built around the Ideal Cut as the top grade, the new system will allow a 37% growth in the amount of stones that could possibly get an AGS zero, although the Ideal is still in the top category.

Like the GIA, the AGS is moving away from the old proportion-and-numbers model and now includes three new subcategories that will designate an AGS Triple Zero: light performance, proportion factors and finish.

All in all, while we still have our misgivings about whether cut can really be graded, we do find the idea that these two institutions are moving together on this issue heartening.

AGS’ decision to grade square-cut princesses is more problematic. Many consumers don’t realize that the princess is not a set, fixed shape. Many cutters still experiment with what they consider a “princess.” With that variation from the get-go, it’s hard to see how anyone could issue numbers that say that one princess is better than others.

Finally, all this emphasis on cut should not lead consumers to think that cut is the most important thing in grading a diamond. Cut is important. But so are the other three C’s. And consumers ignore them — just as they at one time ignored cut — at their peril. 


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