EGL USA Announces Indicators For Lab-Grown Diamonds

As lab-grown diamond technologies progress, gemological labs are constantly seeking ways to detect such diamonds. Recent developments in CVD (Chemical Vapor Deposition), gem-quality laboratory-grown diamonds, has led EGL USA to finding three early indicators that gemologists and equipped laboratories could potentially use to screen for CVD diamonds.

According to EGL USA the three early indicators, presented at two Canadian jewelry trades shows are:

1. Fluorescence under short-wave ultraviolet light (yellow-green) was one or two degrees stronger than under long-wave UV.

2. Most of the CVD diamonds studied had clouds of white particles, which tended to show up in one plane. These inclusions can show up in natural diamonds as well, but tend to be more dispersed.

3. Cathodoluminescence colors (when stones are exposed to strong beam of electrons) are different than colors in natural (mostly blue) and synthetic HPHT (mostly green). 

Branko Deljanin, Director of Canadian Operations and an HPHT expert, recommends that in case the first two indicators are present, the gem in question should be sent to a professional lab for further study. “Our findings are based on very limited research samples, but we are optimistic that we will solve the detection challenges,” says Deljanin. Other characteristics of the limited sample studied by EGL USA researchers were:

• Clarity of polished CVD diamonds studied were slightly included to very slightly included

• All stones were fancy shapes or irregular (not round)

• Weights were up to 0.45ct, depth up to 2.50mm

• 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 absorption peaks in VIS-NIR spectra Photoluminescence could detect very low-level impurity states within the crystal structure.