The International Gemological Institute (IGI) has established a set of procedures for successfully separating fancy-colored natural diamonds from synthetics, which can often be difficult to screen due to treatments.
The lab came up with a method for screening each color category using advanced techniques such as Fourier transform infrared spectroscopy (FTIR) and photoluminescence spectroscopy, together with magnification, it said last week. Traditional screening devices generally use photoluminescence to capture a diamond’s fluorescence and phosphorescence under ultraviolet light. However, that method often doesn’t work with fancy-colored lab-grown because the stones may be treated with irradiation, heat and pressure, which alters their fluorescence and phosphorescence, IGI explained.
The new method can be used to distinguish between loose natural and lab-grown, as well as those mounted in jewelry.
“With lab-grown fancy-colored diamonds gaining momentum and the differential pricing being substantial, it’s imperative that the screening is done by a reputable laboratory,” said IGI CEO Tehmasp Printer. “We had a few cases in recent times where there has been a contamination of natural fancy-colored pink diamonds mixed with lab-grown pink diamonds.”
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Main image: A lab technician using FTIR spectroscopy to screen fancy-colored diamonds. (International Gemological Institute)
