GIA to Assess Cut on Reports

They’re not calling it a cut grade, but the Gemological Institute of America will add a cut “classification system” to reports this spring, officials say.

“It’s a big change, a huge leap forward for GIA, for the industry, and for consumer protection,” says GIA president William E. Boyajian.

At press time, Boyajian did not yet have specifics on how the system will be derived or presented—simply that it will classify “cut” in a way that both the trade and consumers can understand. “Whatever we do, it will be practical, simple, and clear, but not oversimplified to the point that it becomes meaningless or defeats the science,” he says. “We are still working through how we should present it. Do we do it the way we look at polish and symmetry? Or do we do it with graphic images that show where a particular stone is in relation to some kind of hierarchy? We don’t have all the answers, but there’s no question that we are going to be establishing certain ‘calls’ on cut, far more than we’ve done in the past.”

One thing there will not be is a cut grade that measures how a stone fits into a fixed set of proportions such as those offered by the American Gem Society, which uses as its base Marcel Tolkowsky’s “Ideal.” “For years, the only thing that people could hang their hat on was the Ideal,” Boyajian says. “This will give cutters new goals to shoot for. It will validate a lot of the good cutting that’s been going on.”

GIA also is considering logging how much “fire” and “brilliance” each stone has, based on its recently derived numerical calculations for those qualities, and may lump the two qualities together.

Boyajian also said GIA will take into account the “taste factor.” “Whether you want more fire or more brilliance depends on taste,” he says. “We want this to be similar to our colored stone grading—it’s hard to say there’s one best color. We want to express cut in a similar manner. We are not trying to say this is the best and the rest is no good.” Badly made stones, however, will be “flagged.”

The new system is being developed only for round brilliants, although the research eventually could have implications for fancies. Boyajian stresses that the Institute is treading carefully, since any decisions in this area could have wide-ranging effects. “There is anxiousness to make sure what we do is correct and doesn’t shake up the markets,” he says. “When we do decide, I’m sure it will be the shot heard round the world.”

Latest research. The new classification system stems from GIA’s research on cut. The latest report from that study appears in the Fall 2001 issue of Gems and Gemology and focuses on fire.

The study introduces a fire-tracking metric called “dispersed colored light return” (DCLR), which allowed researchers to gauge the fire in 26,000 “virtual” stones. The computer-modeled diamonds were inclusion-free, colorless, and perfectly symmetrical.

Among the discoveries:

  • No single set of proportions yielded the most fire. GIA reached a similar conclusion regarding brilliance. Boyajian says this discredits the notion of an Ideal cut.

  • While some cuts—including the Ideal—had strong fire and brilliance, the two qualities were often in opposition. For example, smaller crown angles boost brilliance, but larger crown angles, along with smaller tables, increase fire.

  • The lengths of star- and lower-girdle facets affect both fire and brilliance. GIA notes that most previous cut studies, as well as cut grades, don’t take this into account.

  • Lengthening lower girdle facets from Tolkowsky’s value of 50% to 75%-85% enhances a stone’s fire.

“A lot of the anecdotal things we used to talk about have been validated scientifically,” Boyajian says. “You can’t have the most fire with the most brilliance. There is no one best cut.”

The final part of the study, which explores scintillation, should be completed next year.

AGS response. Meanwhile, American Gem Society lab director Peter Yantzer says that he welcomes more competition in the cut arena. “One of the tenets of the American Gem Society is protecting the consumer, so if GIA wants to provide more information on their reports, I commend them for that,” he says.

As for GIA’s disparagement of the Ideal concept, Yantzer says, “Our grading system has always been dynamic. And if more information becomes available to us either through our own studies or through GIA research, we are always willing to rethink things.” But he doesn’t see changes arising out of what’s appeared so far. “I still feel that, when all is said and done and GIA finishes the research, they will end up with a stone that’s close to the Tolkowsky model,” he says.