Round Diamonds – The standards for quality of cutting a round brilliant diamond have been established by AGS using nearly 100 years of research. AGS Laboratories assign a numeric cut grade; 0 to 10, 0 being best, complete with all the proportions and finish parameters for round diamonds.
Fancy Diamonds – Since the proportions for fancy-shaped diamonds vary the optimal balance of luster, brilliance, dispersion and scintillation, is different for each shape. Therefore, no cut grade is assigned for fancy-shapes at this time. Research is currently underway by the AGS for the future potential in offering a cut grade for fancy-shaped diamonds.
Terminology
Ideal Cut A diamond cut to optimal proportions, with optimal polish and symmetry, with the most weight loss to produce maximum luster, brilliance, dispersion, and scintillation. Diamonds cut to this standard are the most valuable, with only 5% of the round brilliant diamonds on the market cut to this standard.
Well-Cut Diamonds that have very good optical beauty that fall just outside of the parameters of Ideal Cut diamond. These diamonds are priced less than Ideal cuts because they are not as rare.
Deep Cut This diamond will appear smaller than it weighs because it’s weight is retained in the depth. It is cut with a deep pavilion (bottom of the diamond) that does not reflect light back through the crown (top of the diamond). Light leaks out the pavilion producing a dark appearing diamond that lacks beauty. These diamonds are sometimes called nailheads due to their dark, face-up appearance.
Shallow Cut Diamonds that are cut with shallow pavilions that do not reflect light back through their crown. The light leaks out from the pavilion, producing a washed-out or watery appearance that is not beautiful. Weight is retained in the diameter, making the diamonds appear larger than they weight. These diamonds are sometimes called fisheyes, due to unsightly reflections in the crown area.
Bow-Tie Effect dark area in the center of some fancy-shaped diamonds. A large bow-tie in the center of a fancy shaped diamond detracts from beauty and lowers the value.
Cut in Relation to Value
Cut is the most important factor to a diamond’s beauty. Regardless of the color, clarity, and carat weight, a well-cut diamond will be beautiful. Cut is so important to the value of a diamond that it can affect the value by 25% to over 50%.
Fancy-shaped diamonds, since they retain weight from unusual shaped rough crystals, are often less expensive then comparable round diamonds. Carat for carat, since fancy-shaped diamonds are elongated, they appear larger than round diamonds. If a consumer is interested in maximizing size appearance, they can buy a smaller, yet larger-appearing fancy shaped diamond of the same quality for less than a comparable round brilliant diamond.
When shopping for a diamond, ask a professional American Gem Society jeweler about diamond cut quality. Physically examine diamonds with your own eyes, shop and compare, and make the best decision for you.