Professional Jeweler Archive: Sleuthing for Synthetics

September 2000

Diamonds: Gemology

Sleuthing for Synthetics

A recently discovered feature could make it easier to detect synthetic diamonds

The detection of near-colorless synthetic diamonds might just have become easier. The reason: discovery of a distinctive luminescent band at 693.7 nanometers using SAS2000 Raman photoluminescence spectroscopy.

The complicated language means simply the Raman equipment has revealed a feature in synthetic diamonds never known to be reported before. The test results are preliminary, cautions Martin Haske, president of Adamas Gemological Laboratories, Brookline MA, who first spotted the feature in late July. But they’ve caught the attention of other gemological laboratories.

“We’ve studied 46 near-colorless synthetic diamonds from Russia,” says Haske. “The photoluminescent feature at 694nm was discernable in over 70% and very easily seen in over 30%.

“The existence of the feature apparently correlates to shortwave fluorescence/phosphorescence present in the synthetic diamonds.” In other words, when Haske detected fluorescence or phosphorescence in the stones, he also detected the spectroscopic peak.

The synthetic diamonds came from Chatham Inc., San Francisco, CA, and Morion Co., Brighton, MA. Haske hopes other synthetic diamond producers – including Sumitomo, General Electric and De Beers – will supply his lab with samples for further study.

Mixed Response

Other gem labs around the world have weighed in with various thoughts on the report. SSEF Laboratory in Basel, Switzerland, also detected the feature in some synthetic diamonds, but says it’s too early to make a definitive statement.

At the Gemological Institute of America in Carlsbad, CA, a spokesman says the feature was not present in colorless synthetic diamonds observed there. “It needs further investigation to determine the significance with regards to an identification criterion,” says the spokesman.

Dr. Emmanuel Fritsch of the University of Nantes in Nantes, France, hasn’t performed any testing but appears to approve of Haske’s methodology. “It may not be a 100% criterion [for all near-colorless synthetic diamonds], but it’s a correct observation for many stones of a certain category, so the finding deserves attention. Providing [Haske’s] work is correct, the 693.7 line is a strong indication for synthetic origin.”

Alternate Detection Methods

Other gemological tools are available to test for synthetic diamonds. Because the synthetics contain metallic inclusions, most of these tests check for electrical conductivity.

In addition, De Beers’ DiamondSure and DiamondView machines are available, though they aren’t used widely.

Haske says the new Raman spectroscopy test, if confirmed, would simplify and enhance the arsenal of tools needed to detect near-colorless synthetics.

– by Robert Weldon, G.G.

The luminescent band at 693.7 nanometers on this SAS2000 Raman photoluminescence spectroscope printout may help to identify near-colorless synthetic diamonds. The near-colorless synthetic diamonds shown below are courtesy of Tom Chatham of Chatham Inc., San Francisco, CA.

Copyright © 2001 by Bond Communications