GIA Spots Synthetic Ruby with Filling Treatment

RAPAPORT… The Gemological Institute of America (GIA) has identified a laboratory-grown ruby filled with lead glass — a rare phenomenon, as the trade mostly uses this method to improve natural stones.

The transparent to semitransparent, oval mixed-cut piece weighing 3.53 carats was submitted to the GIA’s lab in Carlsbad, California. Examination under a microscope showed it contained a network of fractures featuring a “blue and orange flash effect” — proving the treatment’s presence, the GIA said.

“We commonly see glass-filled natural rubies, but to our knowledge, only one other laboratory-grown example has ever been submitted,” wrote Forozan Zandi, a staff gemologist at the Carlsbad lab, in the spring 2021 edition of the GIA’s scientific journal, Gems & Gemology.

Lead-glass filling means adding a substance with a refractive index very close to that of the host material, thereby minimizing the appearance of fractures, Zandi wrote in the article, which the GIA published this month. This treatment can upgrade the clarity of low-quality stones, making them usable in jewelry.

“While it is unclear why anyone would go to the trouble to treat a synthetic ruby with lead-glass filling, gemologists should be aware that such material does exist in the trade,” she noted.


Image: The synthetic ruby with lead-glass filling. (Diego Sanchez)