The clarity of a diamond is judged under a microscope. Its color is judged when it is upside down. You cannot see weight. What you see when you look at a diamond is its size and its light performance. Light travels, so you can judge the light performance of a diamond from all the way across the room.
While light performance is the most visible aspect of a diamond’s beauty and value, there is no perfect way to measure it. Without question, the system developed by the American Gem Society (AGS) is the most scientifically vetted. To our knowledge, only the AGS has published its research in scientific journals outside of our own industry.
The AGS method relies heavily on mathematical calculations, which have the advantage of being repeatable and consistent, but may not fully appreciate the effect of crystal transparency. Transparency and the clarity grade of a diamond are two different things. And while extremely poor transparency is sometimes noted on the grading report, transparency is usually ignored, even though it may affect the light performance of any diamond.
Despite the transparency issue, the AGS system remains the best method available today for assessing the light performance of a diamond.
There are a number of technologies that purport to measure the light performance of diamonds directly. One problem with direct-assessment approaches is that the results tend to be biased to the specific illumination and other hardware constraints of the system. They also tend to be sensitive to the precise orientation of the diamond when placed in the system, which can cause repeatability problems and misinterpretations of glare. We are not suggesting that these technologies lack merit. The majority of companies behind them are composed of individuals with integrity, dedicated to improving our understanding of diamonds. However, we believe their results should be taken in combination with other factors.
Neither the Gemological Institute of America (GIA) nor AGS considers these results when assessing the cut of a diamond.
It is telling—damning, in our opinion—to point out that a cubic zirconia always outscores a diamond in these environments, yet a cubic zirconia lacks the internal light reflection, the life, and fire of a diamond. Experts can spot a CZ from across the room.
The GIA, meanwhile, has adapted a system that seems intentionally loose. Approximately 85 percent of modern-cut round diamonds flowing through the GIA labs each year receive a cut grade of Excellent or Very Good. The color and clarity scales produce exactly the opposite results. Only a very few diamonds receive the top grades.
Why would the GIA create such a loose cut-grading system? And why revert to a parameter-based system when its own research demonstrated that it is the “relationship between all the facets in a diamond” that matters, rather than any one set of parameters?
Perhaps the GIA feared becoming a niche lab like AGS? Let’s face it: No one sends a diamond to the AGS unless they believe it will receive a top score for cut, which in a strict system is by definition a small percentage.
The GIA remains the world’s largest and most influential grading lab, providing a powerful voice for science and consistency on critical matters such as standards for color and clarity grading, legal disclosures and definitions, etc. A smaller GIA would not be good for the industry. The fact that the GIA never expanded its light performance research beyond 58 facet rounds, however, is a clear indication that it preferred to leave the intricacies of a finely tuned cut-grading system to others.
The AGS can assess the light performance of any diamond regardless of shape or facet arrangement. Amazingly, the light performance–based system the AGS has promoted for more than 10 years still surprises many, even otherwise knowledgeable, diamond buyers.
Google “ideal cut diamond” right now, and, no doubt, you will be led to a chart featuring the AGS cut standard originally adapted in 1967, based upon the work of Marcel Tolkowsky, circa 1919. This system was debunked by both the AGS and GIA path of light studies. It’s not that the old Tolkowsky system is completely wrong, it’s just not completely correct.
There are many ways to cut a beautiful diamond. And the AGS ASET map is the clearest method available today to understand the resulting light performance. All Fire and Ice diamonds over 0.3 ct. are accompanied by an AGS Proprietary Light Performance Grading Report, complete with an ASET map to describe the individual light performance of each diamond.
One look at the ASET maps consistently produced by the patented Fire and Ice design is all that it takes to understand superior light performance. Fire and Ice diamonds are truly brilliant beyond compare.