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  • The four stones that were sent into GIA’s Carlsbad lab as natural sapphires. GIA determined they were, from left to right, a 48.63-carat piece of man-made glass, 9.17-carat and 6.21-carat lab-grown sapphires, and an 8.46-carat natural blue sapphire rough.(Photo courtesy: GIA)

GIA Found Synthetics, Simulant among Four ‘Natural’ Sapphires


The Gemological Institute of America (GIA) recently received a group of four ‘natural’ blue gems for identification and origin reports, which was submitted as natural sapphires, and the results came out surprising. 


Among the four ‘natural’ gems, two were found as synthetic and one as a simulant. 


GIA reported in its Summer 2022 Gems & Gemology issue that its Carlsbad lab recently received four rough blue stones submitted as natural sapphires for identification and origin reports. 


According to GIA, the largest weighed 48.63 carats, which was partially fashioned with evidence of polish lines on its surface. Examination under a microscope revealed gas bubbles, distinct flow marks, and conchoidal fractures, while the polariscope revealed weak snake pattern bands. Its hydrostatic specific gravity (SG) was 2.48. 


GIA said that all these observations together suggested a glass imitation, which was confirmed by comparing the infrared spectrum with that of man-made glass. 


Two of the other submitted blue stones, weighing 9.17 carats and 6.21 carats, were more convincing imitations of natural sapphire,” GIA said.


The final piece of rough in the parcel, an 8.46-carat stone, had a frosted surface that made it difficult to see inside, but the GIA observed some natural-looking fingerprints and strong, straight inky-blue banding. The lab confirmed the stone was a natural sapphire from Madagascar that had been heat treated.


This was an interesting study of how synthetics and simulants can be mixed with their natural counterparts to misrepresent a parcel,” the GIA explained. However, careful examination and standard gemmological testing are usually enough to identify them correctly.”





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