By
Ashley Bailey 
, Wednesday, August 02, 2006 12:00 AM
The American Gem Society, which has been grading round brilliants for cutting since 1996, will begin to grade fancy cuts in 2005.
The first shape for which it will offer what it calls cut quality analysis is the highly popular princess cut, a square shape introduced in 1981 as an alternative to the radiant rectangle cut.
As it does with round brilliants, AGS will divide its princess cut grade into three parts: light performance, proportion factors and finish—each with a high rating of Zero and a low rating of 10. However, ratings will be based on criteria developed for this specific cut. Once it develops criteria for other cuts like the marquise and pear shape, it will start to issue cut quality analysis reports for them also. Stones that earn zeros for all three grade components will earn "zero ideal" grades for their cut category.
"Light performance" is the most revolutionary new addition to AGS cut grading methodology. In the past, AGS judged stones for craftsmanship with the assumption that fine workmanship automatically translated into high performance.
Now AGS will test stones to see how they actually behave with regard to brilliance and fire. It will do so by, first, scanning stones with a Sarin proportion measurement machine, then translating this information into a 3D computer simulation and, last, doing a ray-tracing analysis of the virtual diamond to measure its light-handling capabilities.
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