Whiteflash-Diamond Playground

You have no doubt seen this on many of our ‘A Cut Above’ reports:

If you have wondered how the final American Gem Society Lab grade is determined, the cut grade has three factors and the lowest determines final grade.

Light Performance is a cumulative grade (added up). It is the sum of all deductions for Brightness, Contrast, Dispersion & Leakage. If the total deductions are < 0.50 the LP grade is 0. If 0.50-1.49 the LP grade is 1. If 1.50-2.49 the LP grade is 2 and so on.

Proportion Factors is part cumulative (girdle thickness, culet size) and part net-lowering (durability, weight ratio, tilt). If the girdle and culet both have deductions of 1 the PF grade is 2. If there are no cumulative deductions but weight ratio and tilt both have deductions of 1 the PF grade is 1 (b/c those are net-lowering deductions). If there are no deductions the PF grade is 0.

Finish (polish & symmetry) is net-lowering. Polish can be 0 and symmetry can be 2, which would result in a finish grade of 2. Polish and symmetry can both be 2, which would also result in a 2. If the polish grade is 5 and the symmetry grade is 0 the finish grade is a 5.

The cut grade is the lowest grade (net) between LP, PF and Finish:

Light Performance 0
Proportion Factors 0
Finish 1                       
Cut grade = AGS1

Light Performance 3
Proportion Factors 0
Finish 0                      
Cut grade = AGS3

AGSL is extremely hard on finish, which we think is a good thing.  Some dealers will advertise “AGS0″ diamonds but they will have been sent to GIA and received EX or VG in finish.  Those diamonds should not be advertised as AGS0.  If fact, with the new light performance grading the only way you can call a diamond AGS0 is to send it to AGSL.  Otherwise it is false advertising.