Lab Notes

Screening of Mounted Melee Using the GIA iD100

Paul Johnson and Stephanie Persaud
August 25, 2017
Diamond ring with 100 melee side stones.
Figure 1. A diamond ring with 100 melee side stones incorporated into the setting. Photo by Sood Oil (Judy) Chia.

As previously reported in the G&G Lab Notes section, significant amounts of melee-size synthetic diamonds, both HPHT- and CVD-grown, are being manufactured for the jewelry industry. Over the past year, we have seen more instances of synthetics incorporated into finished jewelry pieces.

Recently in GIA's New York laboratory, we examined a diamond ring with 100 colorless melee side stones, each about 0.5 mm in diameter (figure 1). Using the new GIA iD100TM screening device, we were able to screen these melee. The device uses sophisticated spectroscopy technology to distinguish natural diamonds—either loose or mounted—from synthetics and simulants. The operator simply points the probe at a diamond, and the result is given within two seconds. Out of the 100 melee from this ring, one stone was referred by the GIA iD100 for further testing (figure 2).

One stone was referred by the iD100 for further testing.
Figure 2. One stone, about 0.5 mm in diameter, was referred by the GIA iD100TM for further testing. Photo by Sood Oil (Judy) Chia. The inset photo shows a prototype of the iD100.

Upon further examination, the stone was determined to be a type IIa diamond (no detectable nitrogen impurity). Examination in the DeBeers DiamondView instrument revealed strong phosphorescence to short-wave UV radiation, typical for HPHT-grown synthetic diamonds (figure 3). Further examination using photoluminescence (PL) spectroscopy detected a very weak silicon impurity and a very high concentration of nickel, often a catalyst used to grow HPHT synthetic diamonds.

Synthetic melee showing phosphorescence.
Figure 3. The referred melee displayed strong phosphorescence to short-wave UV radiation, as is typical of HPHT-grown synthetic diamonds. Image by Paul Johnson.

This ring offered an excellent example of how the GIA iD100 can quickly screen very small mounted diamonds and accurately detect any synthetics or even simulants.

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