The diamond industry is at the beginning of a “new diamond age,” European Gemological Laboratory gemologist Sharrie Woodring said at a talk on “A Jeweler’s Guide to Man-Made Diamonds.”
The difference between synthetic diamonds and previous imitations, she explained, is that synthetics are chemically and scientifically identical to a natural diamond. The only difference is that they’re grown in a lab rather than in the Earth. Under the law, they have to be disclosed as man made.
She noted that there are two methods for creating synthetic (or lab-grown) gems: high-pressure and chemical vapor deposition.
Most of the synthetics now being produced are colored stones, she said. “No company that I know of is selling commercial qualities of colorless synthetic diamonds. It is still not really cost effective, because it takes longer to grow a colorless diamond than a colored diamond. People have been able to grow high-quality CVD single crystals, but they re extremely expensive to produce.”
She said some researchers at the Carnegie Institute of Washington recently announced a breakthrough in high-speed CVD growth. “This has a lot of potential, but it’s not here yet,” she noted.
Here are some of the ways to identify synthetic diamonds:
* Metallic inclusions. Synthetic stones can often be picked up with a magnet.
* Color zoning. The color in the stones often grows in distinct patterns.
* Internal graining. “You see the boundaries between the growth sectors,” Woodring said.
* Shortwave fluorescence stronger than long wave. This is a good indicator. In addition, when you turn the light off, sometimes a synthetic will continue to phosphoresce.
None of these signs is definitive, Woodring noted, just a sign that the stones should be sent to a lab for further testing. “If you have a stone and you don’t know what it is, send it to us,” she said.
She noted there are machines on the market that detect synthetics, but at present they carry a high price tag.
As far as terminology questions, she said her lab and the Federal Trade Commission consider “lab-grown,” “synthetic,” or “created” acceptable. “People consider ‘synthetic’ confusing to consumers,” she said. “They think it means imitation.”