Cutting Grades Two Years Off

The AGS will wait at least two years on its decision to provide cut grades as the organization's board considers the technology needed to measure a diamond's 'performance', writes Russell Shor.

The American Gem Society (AGS) is still far from finalizing comprehensive cut grades for fancy shaped diamonds, says the Peter Yantzer, director of its grading lab. The two additional years is far longer than originally planned because the AGS board, which supervises lab activities, found that a great deal of hard science is necessary to supplement the myriad of trade opinions they’ve received.

Yantzer says the AGS diamond board, which establishes and regulates its diamond grading standards, is still looking at a number of technologies designed to measure diamond "performance" - the amount of light and fire reflected through the crown.

He added evaluating such technologies "isn't easy because they all employ a different approach to the problem. " The lab could combine several approaches if one cannot do the job. A decision is expected, perhaps optimistically, by the middle of next year. From there, tests will take another year. "It will probably take a year to put everything together then verify to see how it all works in a lab setting."

"We've seen several proposals from different groups," says Yantzer. These include Diamond Technologies in Macon, Georgia; Eight Star Diamonds from California; and the MSU Center in Russia. Yantzer says such technology will be necessary to provide the most complete analysis of diamond cut, but thus far "most of the technologies we've looked at address only brilliance and not dispersion." Dispersion is the breaking down of white light into various spectral colors.

The Gemological Institute of America, which has been conducting its own research into diamond performance, has said that developing methods and standards for measuring dispersion and fire is extremely difficult.

Once the AGS decides on a technology to measure diamond performance, the lab's staff will use the data to compare it against results from polls it has conducted of member retailers and diamond people rating which proportions are the most attractive for various cuts.

Two years ago the GIA released the first part of its diamond study, which challenged the long held notion that a single set of "Ideal" proportions delivers the most dynamic diamond. Instead they've found that varying the crown and pavilion angles and table percentage resulted in a broad range of very brilliant diamonds. Critics of the study argued that the study did not yet measure fire and dispersion, two very important factors in a diamond's appearance, and that only the best proportions of all three factors would yield the optimum balance. Last summer the GIA announced that preliminary results from its continuing research on the subject still supported its "multiple proportion sets" theory, though the range was somewhat narrower.

Yantzer says that if the GIA finds that there are indeed multiple sets of Ideal proportions, the AGS would consider revising its system for grading the proportions for round diamonds, which it developed about 30 years ago. That system awards the top grade of 0 for proportion, symmetry and finish. The top proportion grades go to diamonds adhering closely to the formula that Marcel Tolkowsky developed in 1919.

"If there's new technology that helps you better understand things, it's only right to adopt it, even if it doesn't agree with our current grading system," says Yantzer.

He firmly believes, however, that the AGS "0" proportion grade will stand up under any technological development. "It's an absolutely beautiful stone. Nothing would negate that."

Much of the business for AGS is due to it's being the only major gemological facility to issue a detailed cut grade. "We've added a number of people to keep the turnaround at five days," noting that the lab in Las Vegas, Nevada, now has a staff of 40. If other sets of proportions equaled the "0" grade, it would be a boon to business at the lab. "We'd love to see this. Our business would increase exponentially," Yantzer said.


This article was published first in GEMKEY and updated 10/3/00.