Laboratory gemologists at the European Gemological Laboratory (EGL) USA have found a simple positive identification feature in all Chemical Vapor Deposition (CVD) laboratory-grown diamonds, says Branko Deljanin, EGL USA’s director of Canadian operations.
The new Apollo CVD Diamonds they have examined show an orange-brown color when the stones are exposed to a strong beam of electrons (Cathodoluminescence), Deljanin says. Natural diamonds will show mostly blue color, and HPHT synthetic diamonds show mostly green color. Having such a definitive test could give professional laboratories a quick and reliable method to separate out CVD diamond from natural and other synthetic diamonds.
This is important since Apollo Diamond’s gem-quality CVD diamonds will reportedly be available in limited quantities late this year. EGL USA has been studying a small sample of these diamonds on loan from the manufacturer.
“Our findings are based on very limited research samples, but we are optimistic that we will solve the detection challenges,” said Deljanin, who will be studying more Apollo diamonds over the next few months. Preliminary studies were based on five samples. “We are working with Apollo on both detection and disclosure issues and plan to release a more comprehensive, definitive report that will provide assurances to the trade about these lab-grown gems.”
Deljanin gives tips to the retail jeweler that you may have a CVD diamond if you see yellow-green fluorescence under short-wave ultraviolet light that is one or two degrees stronger than under long-wave UV, and you see clouds of white particles in one plane. These inclusions can show up in natural diamonds as well, but tend to be more dispersed.
Should these two indicators be present, the gem in question should be sent to a professional lab for further study, Deljanin says. “Very low nitrogen concentration and clean stones make them extremely difficult to identify,” he says. As with HPHT, identification of CVD diamond requires advanced instrumentation to conclusively identify the high-quality single crystal CVD diamond.
Characteristics of the limited samples studied by EGL USA researchers are:
* Clarity grades of polished CVD diamonds studied were slightly included (SI) to very slightly included (VS)
* All stones were fancy or irregular shapes (not round)
* Weights were up to 0.45 ct., with depths measuring up to 2.5 mm
* Almost all samples are type IIa (one was a combination IIa /Ib)
* Colors are fancy light brown to near colorless, and, according to Deljanin, might be improved with HPHT
No characteristic spectrum in the visible or near infrared spectra
For more information about CVD diamond identification, contact Branko Deljanin, at EGL USA’s Vancouver lab, at (604) 630-0464.