AGS vs GIA – More Grading Results

Last week, we sent two GIA certified stones to the AGS lab. The reason being was that the GIA both gave them a “very good” cut grade, despite them being what we thought top stones deserving of a higher cut grade.

The reason they were given only a very good cut grade from the GIA was that they both had a 40.4 pavilion angle. So whilst the GIA favours deeper pavilions, these stones, with their shallow pavilions were unfairly penalised. It’s worth noting however, that we wouldn’t consider any stone for our inventory with a pavilion angle lower than 40.4, as generally speaking, there would be a slight “fish-eye” effect (darkness under the table).

However, with both stones having a 35 degree crown angle and a 40.4 pavilion angle, they were what we considered to be top performers, so we sent to the AGS for grading.

The first stone was graded by the GIA as a 1.03ct, E/SI1 with a very good cut grade, excellent polish, excellent symmetry and no fluorescence. This was then regraded by the AGS as a 1.03ct, E/SI1 with an ideal cut grade, ideal polish, ideal symmetry and negligible fluorescence.

The second stone was graded by the GIA as a 1.06ct, F/SI2 with very good cut grade, very good polish, excellent symmetry, faint fluorescence.  This stone was regraded as a 1.06ct, G/SI2 with an excellent cut grade, ideal polish, ideal symmetry and negligible fluorescence. The excellent grade was due to a “weight ratio” deduction.

The good news is that these two stones were both purchased at “very good” cut grade prices, so the 1.06 G/SI2 at least, is at an excellent price (no pun intended).

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