Developing a grading system for diamonds is an ongoing process that reflects advanced technologies, cutting skills, and changing tastes, said Peter Yantzer, executive director of the American Gem Society Laboratories, during a presentation on Wednesday titled “Understanding AGS Cut Grades.”
“It’s a dynamic process,” he told the audience. “Not a static system. It combines science and technology. It changes, and change is a benefit of the process.”
Yantzer’s talk included a history of cut grade standards, current standards, examples of AGS cut grade certificates, and examples of how the grading process is applied.
Yantzer stressed that consumer protection is the focus of the grading system. “If you protect the consumer, you protect the supply and distribution of the entire jewelry industry.”
The American Gem Society Laboratory was founded in 1995, and its cut grading reports are based on grading standards first developed in 1955 and implemented worldwide. Yantzer, who began work in the early 1970s as the seventh gemologist to work at the Gemological Institute of America’s New York office and later served as director of GIA’s laboratories in Los Angeles and Santa Monica, has witnessed many of the advances in cut grading. He noted that AGS and GIA are sister organizations that were both founded by Robert M. Shipley.
The last AGS revision of its diamond grading standards was in 1999, Yantzer said. The standards include the following measurements:
* Crown angle to a tenth of a degree;
* Pavilion depth percentage to the nearest tenth of a percentage;
* Pavilion angle, which supersedes depth percentage;
* Spread pavilion, which is a technique that can spread the pavilion beyond AGS grading standards without having a detrimental affect on the overall grade; and
* Culet size.
Yantzer noted that many other variables go into the grading process, and the relationships among standards create other variations in grading. For example, a 2% difference in the crown angle, while visually unnoticeable, makes an extreme difference in the performance of a diamond.
In addition to the many grading variables, AGS Laboratories places a large emphasis on the cutting and polishing of a diamond, he said. “I believe cutting is the most important value of diamond grading. We reward fine cutting. If you can’t cut it and get the polishing right, we’ll grade it down.”
Noting the difficulties of cutting the hardest substance on earth with great precision, he added, “Diamond cutting today is amazingly good. With diamonds you have to finesse it. It’s art and craftsmanship to the max.”