The blue visible light diamonds emitted in different luminous intensities after the exposure of ultraviolet irradiation is called fluorescence. If they still emit visible light without ultraviolet source, this luminescence property is phosphorescence. The distinct differences between the fluorescence and phosphorescence luminescence images of natural diamonds and their synthetic counterparts have provided a base for screening synthetic diamonds in a simple and fast manner which, to some extent, helps eliminate the trade’s fears of undisclosed synthetics, sustain the integrity of the diamond pipeline and build trading confidence.
China’s Biaoqi Electronics Technology Co, Ltd launched the self-developed GLIS-3000 Gem Luminescence Imaging System in October 2015. The device screens diamond samples by analysing luminescence properties of fluorescence and phosphorescence images for HPHT and CVD synthetic diamonds at a speed from seven to 10 seconds per testing.
Regarding the device’s verification criteria, the company’s general manager King Song explained that generally natural diamonds emit blue-white fluorescence with no phosphorescence, while synthetics show blue phosphorescence. Specifically, most of the HPHT synthetics have blue-green fluorescence and high-intensity blue phosphorescence, whereas CVD synthetic diamonds emit fluorescence and phosphorescence in other different colours. Diamonds that release yellow or green fluorescence or phosphorescence need further testing.
According to Song, GLIS-3000 is user-friendly with only one button to complete the whole detection operation. With the measurement area of 7cm×10cm, it can handle batches of loose or mounted diamonds in any shapes and sizes. The minimum measurement size is 0.1 point, and the amount of melees per scanning is over two carats. The large measurement area makes it easy to manage large jewellery samples such as bangles, and locate potential synthetic diamonds from pavé-setting jewellery.
Since launching over half a year ago, Biaoqi has upgraded the device to enable simultaneous screening of fluorescence and phosphorescence, and the enhanced sensitivity makes testing of weak phosphorescence possible. King Song told Hong Kong Jewellery: “GLIS-3000 has been recognised by national and foreign jewellery testing institutes and practitioners after launch. It offers the industry an effective identification method and helps restore the order of the industry.”
Despite the significant performance of testing HPHT and CVD synthetic diamonds with GLIS-3000, Song added, the device cannot detect zircon at present. Regarding the fact that some natural diamonds also emit weak phosphorescence or fluorescence in different colours, while some CVD synthetic diamonds even show the same blue-white fluorescence as their natural counterparts with no property of phosphorescence, he said: “Our GEM-3000 spectral analyser is more reliable for scanning these types of diamonds. Fortunately, as the production of CVD synthetic melees has not been commercialised, melees in the current market are mainly HPHT diamonds that GLIS-3000 is able to identify.”
Talking about the present status of synthetic diamond identification in the industry, King Song said the selling of mixed batch of undisclosed synthetics and natural diamonds has increased the difficulty of testing. It is almost impossible to acquire a completely accurate result with one instrument, while only by integrating multiple technologies and solutions can practitioners confirm the content of diamond samples.
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