Part 2: The AGS Performance Cut Grade System
A New Paradigm in Cut Grading

Think of a diamond as a tiny geometrical sculpture where every facet has a purpose, and the beauty (performance) of the sculpture depends on the precise alignment/angle of each individual facet.   

Imagine what is happening when you are enjoying the dance of light across the diamond. Light from the surrounding panorama enters the diamond and moves through it according to the geometry of the sculpture. A complex kaleidoscope of light emerges — mathematics in motion.



A key insight from this thought experiment is the observation that EVERY facet has a job to do, so every facet contributes to the appearance of the diamond. The whole is the sum of the parts…and then some. 

What this observation meant for the AGS is that old traditional methods for grading cut had to be abandoned in favor of a more scientifically rigorous approach. Traditionally, look-up charts were the primary means of cut grading.  In this approach, all the complexity of the 3-D sculpture was reduced to a handful of numbers representing the averages of various angles and measurements. These few numbers were then “looked-up” in grading charts to determine the cut grade. 

The problem with the traditional approach is that all the geometric flaws and asymmetries of the 3-D sculpture are washed away during the averaging process, so even the most twisted and distorted geometry is indistinguishable from a perfectly cut stone. This is why the AGS looked to other solutions when developing the Performance Grading system. Specifically, if the appearance of the diamond depends on the full richness and intricacies of the 3-D sculpture, then shouldn’t the Cut Grade be based on the same 3-D sculpture, flaws and all?  

The key underlying idea of the AGS Performance Grading system is the observation that EVERY facet contributes to the appearance of the stone. Using state-of-the-art technology, the system uses the actual 3-D model of the diamond and performs a direct assessment of the diamond’s light performance from the model. Because every facet is considered in the assessment, every cutting mistake and design flaw can impact the final Cut Grade. Consequently, the AGS Performance Cut Grade system is the most technologically advanced and scientifically rigorous cut grade system in the world and represents a new paradigm in cut grading.