Power of Gemmology By Prachur Singhal

Figure 1. These 23 HPHT-grown synthetic diamond melee, ranging from 0.002 to 0.012 ct, were identified recently at GIA’s Hong Kong lab.  In recent years, significant amounts of colorless to near-colorless HPHT-grown synthetic diamond melee have been produced for the jewelry industry. As a result, the separation of natural from synthetic melee diamonds has become increasingly critical. GIA offers melee diamond screening services using conventional gemological techniques and analytical methods such as photoluminescence and infrared absorption spectroscopy. In September 2016, GIA’s Hong Kong laboratory received 135 melee diamonds for identification service (see figure 1). Of these, 131 were confirmed to be HPHT synthetics and four were natural diamonds. It is interesting to find natural diamonds mixed in HPHT-dominated groups as “contamination.” The tested melee were colorless to near-colorless round brilliants, ranging from 0.002 to 0.012 ct. Infrared absorption spectroscopy per...

This emerald contains a brown crystal of the rare mineral parisite. There is also an oil-filled cavity showing a blue and orange flash effect, along with two large trapped gas bubbles. This inclusion suite verifies the natural origin of this emerald; it also confirms that the stone, which shows signs of clarity enhancement, is from Colombia.  This short introduction accompanies a chart illustrating some of the characteristic inclusions and other internal features seen in emerald (see above). Over the past 50 years, the observation of inclusions in colored gemstones, particularly emerald, has become an essential foundation for identification, quality analysis, and origin determination. This chart contains a selection of photomicrographs of natural, synthetic, and treated emeralds. It is by no means comprehensive; photomicrographs of features not seen here can be found in many gemological textbooks. The images show the visual appearance of numerous features a gemologist might ob...