Watchdogs

RAPAPORT… How thoroughly can advanced equipment detect whether or not a diamond is natural, or a product of scientific processes?

So many synthetic diamonds are making their way through the global markets that some diamond sellers in the United States express concern, even fear, about the provenance of their goods. The allegedly natural diamonds may, in fact, be lab-grown, and there’s the chance that a few synthetics, by accident or design, got mixed in with natural diamonds somewhere during the process of cutting, polishing, sorting and shipping them to the vendor.

Who can tell the difference between natural and synthetic stones? Can wholesalers, retailers or grading laboratories take accurate measure of the stones in a quick and efficient fashion? These are questions at the heart of an issue dividing the industry, a furor fed by allegations that some synthetics have gone undetected.

“Detection has been on the front burner for GIA [Gemological Institute of America] for a long time,” says Tom Moses, senior vice president of GIA Laboratory and Research. “In 1970, GE [General Electric] produced gem-quality synthetics. Thirty-seven years later, we’re still not intimidated by synthetics, and we feel that they’re identifiable. DiamondSure™ and DiamondView™ are two of the instruments we utilize.”

David Weinstein, executive director of the International Gemological Institute (IGI) in New York City, is confident in the ability of current technologies to do the job. “When you put two and a half thousand stones per day through a lab, is it possible that a ‘G’ could go through as an ‘F’? Yes. But I don’t think the current state is such that synthetics could avoid detection,” he says.

SPECIALIZED METHODS

GIA, IGI and other labs make use of highly advanced equipment, including DiamondSure, to screen diamonds and detect synthetics. Within seconds of a stone being placed on the unit, it is analyzed for signs of a natural diamond; DiamondSure then flashes a message indicating one of two things: natural or potentially synthetic.

If DiamondSure raises a flag about a stone, it’s simply saying, “I’m not sure.” It may have picked up the absence of the 415 nanometer (nm) optical absorption line, one signal that a stone is synthetic. Some natural diamonds, however, lack this, as well. Luckily, there are often structural peculiarities that distinguish a synthetic from a natural diamond, which can be detected through manual spectroscopy on a second detector, the Diamond View.

NO STONE UNTURNED

The stone needs to be cleaned carefully before placing on the Diamond View. The machine’s mid-infrared spectroscopy will help reveal what flux materials or structural quirks are or are not present, displaying the inclusions or shapes in a rotating, full-color, three-dimensional image of the diamond.

There are several obvious tip-offs that a stone is not natural. Because synthetics are grown in pressurized containers, they are likely to contain more than crystallized carbon. A flux material, such as a platinum residue from the container, may be present, or nickel, an even more likely identifier, which is deliberately added in order to help the carbon crystallize. Some synthetic manufacturers claim that they add lead in order to make identification of their product easier, but at least one gemologist, Branko Deljanin of the Vancouver office of European Gemological Laboratories (EGL), suggests they are making a virtue of necessity, by representing an inevitable part of the synthetic-growing process as a step actually intended to help the labs.

Apart from the lead or platinum inclusions, there are likely to be certain structural features in a lab-grown stone. In a synthetic diamond, the decahedron faces will be more developed than in a natural diamond. The process that yielded that synthetic stone is entirely different from the conditions that form a diamond underground. In that natural process, atoms line up in the octahedral faces of the stone. While natural diamonds take many millions of years to be created, it is easy to see why atoms would settle in a different pattern in a synthetic stone produced in a month in a lab at Gemesis or Apollo Diamond.

In the latter case, especially, the differences will be obvious. Apollo Diamond makes use of Chemical Vapor Deposition (CVD) to grow its synthetic stones, and in that process, Weinstein points out, the pressures and growth patterns involved are totally different — technicians are growing the diamonds in thin slabs, wafers really, and there is no way for atoms to gravitate to the octahedral faces, as happens with a natural diamond in a confined space deep within the earth. The slab retains remnants of its growth structure. And in the case of a CVD-produced stone, Diamond View will pick up immediately on the blatant color difference caused by impurities introduced in the growth process. When scrutinized with Diamond-View, an orange-pink coloration marks such diamonds, even though Apollo’s products are explicitly marketed and promoted as “colorless or near colorless.”

As impressive as Diamond View is from a technical standpoint, there are serious drawbacks from the point of view of efficiency. While DiamondSure can analyze and give a read-out for six or seven stones per minute, Diamond View can take half an hour, or longer, for a single stone.

A SPECIAL CASE

There are further limits to DiamondView’s usefulness. It is EGL’s position that the equipment may not be adequate for analyzing mounted diamonds, which often do not physically fit into the machine and are often very small — 0.01 to 0.03 carats — with minor inclusions — VS1 to SI1. The only method that works for all sizes and clarities is the Fluorescence system, according to EGL scientists Dusan Simic and Liz Burnett, who raised the issue in an article circulated by EGL this past spring. Fluorescence involves using sources of light of 365 nm and 254 nm to scan the properties of the mounted stone.

Here is a point of contention among lab specialists. “The use of Fluorescence is very ineffective to separate naturals from synthetics,” argues IGI’s Weinstein. If you are trying to analyze a white mounted diamond, the technique could work, but with a vivid yellow, you could be in trouble. If the short-wave Fluorescence is stronger than the long-wave, then you could safely call the stone a synthetic, because this does not occur in nature. But if the long-wave Fluorescence is stronger, then you are not in a position to declare one way or another. In Weinstein’s view, it is necessary to use mid-infrared and ultraviolet (UV) visible spectroscopy for mounted stones, which are often covered up with metal and which often block the exit path for a light beam. IGI technicians focus their beam and detector right on the diamond, avoiding the nonsubjects.

“Ultraviolet Fluorescence can provide an indication of the origins of some small diamonds, but may not always identify a synthetic,” says GIA’s Moses. He believes in the necessity of doing a combination of tests; microscopes can identify even tiny inclusions, and when combined with other techniques, offer a very high rate of detection.

Peter Yantzer, executive director of the American Gemological Society (AGS) Laboratories in Las Vegas, Nevada, says simply, “We don’t grade any mounted goods—the smallest stone we grade is an 18-point loose diamond.”

While Simic and Burnett express confidence in the fact that “the number of colorless lab-grown diamonds on the market is insignificant,” Yantzer does not take such a rosy view. “I can see a time in the industry when jewelers will be able to say ‘We guarantee that the stone in this ring is a diamond, but we can’t guarantee if it’s natural or synthetic.’” Yet, because AGS lab clients are primarily manufacturers responding to retail demand for their certs, and because it uses advanced technology, Yantzer states that “The odds of a synthetic diamond coming through our lab and escaping detection are infinitesimal.”