A new performance based cut system has been introduced by The American Gem Society (AGS) Laboratories for the emerald cut. In 2005, the AGS introduced a cut grade system for the round brilliant and the princess shaped diamond. New cut grades include the three basic emerald cut shapes: square emerald cut, rectangular emerald cut, and the octagon step cut%%The Performance Based Cut Grade system consists of a ray-tracing software which monitors light’s path traveling through a diamond. The software quantifies the amount and quality of light returned to the viewer in terms of brightness, dispersion, leakage, contrast, and weight to size ratio. In addition to the light performance, the traditional proportions, polish and symmetry of the diamond are considered in determining a final cut grade.%%The AGS has become the industry leader in fancy shaped diamond cut grades, as they are the only major grading laboratory to establish cut grades for princes and now emerald diamond shapes. As its relatively easy to apply the new Performance Based Cut Grade system to different shapes, they plan to introduce cut grades for other fancy shapes in upcoming months.