February 1998

Diamonds: Gemology


Following these simple steps could save your operation

More than a decade has passed since the production of the synthetic Sumitomo diamond. Other labs - including three in Russia - as well as De Beers Industrial Diamond Divisions, General Electric Co. and others have produced synthetic diamonds commercially for industrial use. Yet relatively few synthetic diamonds have been reported in the gem trade. Though that may soon change (see "Growing Carats," p.47), the delay has given the gem trade a head start in nailing down synthetic diamond detection practices.

Photo by Robert Weldon


When buying diamonds for your store, be confident about the goods. Obviously, buying from a known and reputable source is crucial, but always be on the lookout for synthetic diamonds and diamond treatments. Even De Beers views synthetic diamonds as threatening enough to have designed two instruments for quick and easy identification.

The sophisticated DiamondSure and DiamondView detectors measure complex diamond spectrums and fluorescence and luminescence patterns and are now in use at the Gemological Institute of America.

Unfortunately, these instruments are not yet available to those in the trenches - retailers and diamond merchants. Gemologists have gotten used to looking for treatments such as laser and/or fracture filling, but due to the relative scarcity of synthetics in the trade, complacence and inattention could cost dearly. Educating yourself and key employees is a must.

Publications such as the Gemological Institute of America's Gems & Gemology provide continual updates on the progress and detection of diamond synthetics. We'll give you the "Cliffs Notes" version of what to look for.

Green Fluorescence

In short-wave lighting units, weak to strong green fluorescence may be seen in synthetic yellow diamonds, but not always. Synthetic diamonds are generally inert under long-wave fluorescence. The greenish color is rarely seen in natural yellow diamonds, so green fluorescence indicates a strong suspicion of synthetic. Colorless synthetics may sometimes exhibit greenish, yellow or orange fluorescence, but if the stone fluoresces other colors, more tests need to be performed.


If the diamond has greenish phosphorescence or emits light away from short-wave lighting, the stone may be synthetic. Natural stones rarely phosphoresce and then only weakly to moderately, and the phosphorescence does not last long. Colorless diamonds always phosphoresce a long-lasting weak to strong yellow color.


Synthetic diamonds are often attracted to strong magnets due to the metallic flux inclusions. Natural diamonds are never attracted to magnets.

Metallic Inclusions

Always examine a diamond under a microscope. If you see metallic reflections, especially if they're opaque to transmitted light, suspect the stone is a synthetic.

Metallic inclusions do not occur in diamonds, though inclusions of transparent or colorful minerals, such as garnet, often do occur in natural diamonds. In natural diamonds, these inclusions are often accompanied by "stress fractures" (or minute internal fractures associated with the inclusion) which are not present in synthetics.

Size & Color

For the time being gem labs report seeing only small brownish yellow or yellow stones in the 0.10- to 0.25-ct. range coming in for identification. But containing your suspicions to this size and color category may not be enough.

Synthetics are getting larger, more are entering the trade and high-tech synthesis is becoming capable of producing man-made diamonds in various colors. You may never be completely sure about the results of your own examinations. If doubts persist, send the stone to a reputable laboratory for confirmation.

- by Robert Weldon, G.G.

Copyright © 1998 by Bond Communications.


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