Hi,
To determine the quality of diamonds, doesnt mean its GIA or AGS certified means its good. I have visted most of the local retail stores and find that some of them are indeed lousy!! Its just the brand name that carries the diamonds, but doesnt mean its a good piece!
To look at how well/ good a diamond are not only by the 4 Cs - namely Cut, Colour, Carat and Clarity. But how the diamond is cut (Deep/ Shallow/ Ideal) determines the brillance, fire and light return of a diamond. All these can be determine through figures like Table %, Crown Angle, Crown Height %, Pavillion Depth %, Gridle Thickness, Total Depth... etc. I've seen many diamonds, though GIA/ AGS certified is a poor quality diamond!
The certs itself has its own limitations too as it doesnt specify whether its a deep or shallow cut diamond (which will also affect the pricing of diamonds) and "Hearts and Arrows" is also another limitation not specify in the certs. So have to look out for those too.
