Will GIA’s study finally settle the fluorescence question? Don’t count on it.

Even though GIA has found that fluorescence doesn’t usually hurt a diamond’s appearance, old prejudices die hard.

By Rob Bates, Contributing Editor -- JCK-Jewelers Circular Keystone, 9/1/1998

The unsung heroes of the Gemological Institute of America fluorescence study are people who know nothing about gemology. To determine what fluorescence does to diamonds, GIA called upon not just its trained graders, but also its office staffers, who are no more diamond-savvy than the average layperson. This lack of experience was exactly what GIA wanted. With the office workers as stand-ins for typical consumers, researchers asked them if they noticed a difference between diamonds with strong blue fluorescence and ones without it. Most of them didn’t notice a thing.

Then GIA brought in the experts. After examining dozens of diamonds, the trained gemologists didn’t consistently agree on fluorescence’s impact. (The study tested only blue fluorescence, rather than yellow, which is rarer.) And while some thought fluorescence improved a stone’s color in the table-up position, even that was a subject of disagreement. The study, published in the Winter 1997 issue of Gems & Gemology, concluded that except for rare “overblue” stones, fluorescence has no consistent effect on a diamond’s appearance. The findings go on to poke holes in just about every trade objection to fluorescence, including the widely held belief that it “helps” a color grade (see page 148).

Why worry? So if GIA says fluorescence doesn’t matter, and consumers don’t even notice it, why does the trade still fret about it? There are a number of reasons, but the main one seems to be: Old habits die hard. Even with the GIA study, dealers say that strong blue fluorescence generally knocks 5% to 15% off the price of a high-color stone – and makes it a lot harder to sell. “Some people don’t want a strong blue stone, and they won’t look at it even at 20% less,” says Ben Moller, sales manager of E. Schreiber, a New York diamond manufacturer. But ask dealers why, and they’re stumped. “I have no idea,” says Ron van der Linden of Diamex, a New York diamond dealer.

Twisting logic further, for years strong blue fluorescent stones (known until 1938 as “blue-white”) actually carried a premium. (Lower-color diamonds with fluorescence still do.) But dealers say the bias against fluorescence began during the 1970s investment craze. With stones traded “via paper,” graders worried that “strong blues” were really “overblues,” which led to discounts on high-color fluorescent stones. And since many dealers thought fluorescence improved color appearance, they tended to distrust the grades on those stones.

Then came the Korean debacle. Korea had become a major market for fluorescent stones, but in 1993 a muckraking South Korean TV show told viewers that fluorescent stones were worth a lot less than others. Ever since, high-color fluorescent diamonds have been a hard sell not just in Korea, but throughout Asia.

What happens next? So will the GIA study make a difference? In at least one case, it already has. “I had a customer who was hesitant to buy a fluorescent stone,” says van der Linden. “I showed him the Gems & Gemology issue with the study, and it helped immediately.” But New York diamond dealer and publisher Martin Rapaport argues that the markets have their own logic, and the collective wisdom of the diamond industry has already discounted fluorescence. “Studies like this are important, but I don’t know if they will have a big effect,” he says. “If anyone thinks the GIA is right, why don’t they start buying up all the fluorescent stones? There’s a lot of people who would love to sell them.”

Yet some think the bias has already eased a bit. Joseph Schlussel of the Diamond Registry, a New York diamond brokerage, says that with the Asian market less important, so are concerns about fluorescence. Fluorescence is not as disdained in America as it is in Asia. “We try not to buy fluorescent stones, but it’s not a big deal,” says a buyer for one of the largest U.S. retail chains. “If a diamond looks nice, we don’t care if it’s fluorescent or not,” concurs Anthony Fratto of Anthony Jewelers in Palmyra, N.J.

Some note that, ironically, it’s GIA itself that has kept the fluorescence bias alive, by noting it on its lab reports. But Gem Trade Laboratory CEO Tom Yonelunas says the lab lists fluorescence as an “identifying characteristic,” not a grade. Regardless, many tradespeople figure that if it’s on the report, there must be a reason. “It’s become a marketing tool to say my stone is better than yours,” says dealer Bruce D. Verstandig.

The only practical downside to fluorescent stones is that under disco “black lights” they turn blue, and if a woman’s wearing one, she might panic. Yet even dealers acknowledge this is a slim thread to hang a 5% to 15% discount on. “It doesn’t make a lot of sense to me,” says van der Linden.

What’s ironic is that while dealers tend to shy away from fluorescent stones for business purposes, they have no problem using them as gifts. For example, van der Linden gave his wife a diamond with strong blue fluorescence, and he claims many other dealers have done so as well. “Stones with fluorescence tend to have a fine, crispier material in general,” he says. “I have no problem with it.” And some hope that, eventually, the trade will say the same.

What GIA’s Fluorescence Study Ignored

By Gary Roskin, G.G., FGA, Senior Editor

The Gemological Institute of America’s important Gems & Gemology study, described in the preceding article, found that people can’t tell whether a diamond has fluorescence. Diamond dealers who’ve been discounting the price for fluorescent diamonds since the early 1980s are now breathing a sigh of relief. But can they really relax? There’s still the question of a fluorescence-enhanced color grade.

To fully understand color grading, you need to appreciate the often overlooked matter of the light under which grading is done. For more than a century, diamond color grading has been performed in north-facing windows. Is this because north is the direction that the purest diffused natural white light comes from? No. Isn’t the north the only direction where we can avoid any ultraviolet (UV) radiation? No. We use northern light simply because it’s the most consistent of any daytime lighting.

According to Ilene Reinitz, research gemologist at GIA’s Gem Trade Lab, UV has great “scattering” capability. So even though you’re facing north and under the awning and behind the glass, UV is coming through those north-facing windows. The amount of UV varies, of course, depending on the time of day, day of the year, and type of glass.

Robert Shipley Jr., son of the founder of GIA, spent many years researching the most consistent and closest north-daylight-equivalent light bulb, since color-grading diamonds in a retail jewelry store was his main focus. In 1941, GIA produced the first DiamondLite color-grading box. Since then, GIA has found that Verilux fluorescent tubes approximate northern daylight better than any other, and so Verilux has been used in the DiamondLite.

The Verilux light has been very consistent and, surprising to many, contains 6% UV. GIA’s new study used Verilux and three other fluorescent fixtures, one of Phillips’s and two of Sylvania’s equivalents for northern light, which also contain a percentage of UV.

What about the actual color grade? Does strong blue fluorescence, whether perceived by a consumer or not, enhance the color grade of a diamond? Having graded diamonds under Verilux lights that were filtered to remove almost all UV, I have seen diamonds with “Strong Blue” and, especially, “Very Strong Blue” fluorescence appear lower in color than when viewed under “normal,” traditional methods. The difference can be quite dramatic, possibly by two or three color grades. For example, an “E”-color diamond that fluoresces “Very Strong Blue” could be graded “G” or “H” under UV filtered light.

Therefore, you might think that since so many diamonds fluoresce blue to UV, it would be possible to get accurate color grades only by using a pure, diffused white light with no UV.

It is possible to grade diamonds this way. Verilux and other lighting manufacturers offer a 99% UV-free tube for conservancy use. The smallest tube in the UV filtered version is 18 in. and costs $20. There is an inexpensive gel used in stage lighting, but according to Nicholas Harmon, president of Verilux, it blocks only about 80% of the UV.

Certainly a lack of UV would allow a diamond to show its “true” body color without any additional blue fluorescence to enhance the color grade. But diamond graders don’t use UV-free lights. John King, GIA Gem Trade Lab’s director of special projects, explains why.

“Yes, you can create an environment devoid of UV, but it’s a false situation,” he says. “It may sound like the ideal, but it steps outside the practical world. It’s not relevant because it doesn’t really exist anywhere. We try to be sensitive to the practical gemological issues.”

Consistency and tradition are the keys to accurate color grading. Whether at the window, under desk lamps, or in the GIA box, we’ve been color-grading diamonds in light that includes UV – UV that stimulates those fluorescent diamonds to give off a visible blue glow. Remember, all diamonds from a century ago until now have been graded in light that has a small percentage of UV. Says James Shigley, GIA’s director of research, “We have this traditional way to look at diamonds, and that is the benchmark.”