GIA Discovers Lead Glass-Filled Synthetic Ruby

The trade has coped with lead glass-filled rubies, but recently the Gemological Institute of America discovered a filled synthetic ruby it calls “a new low.”

The GIA’s Gems and Gemology eBrief reports that an 11.52 ct. purplish red cushion mixed cut gem was recently taken in at its Carlsbad gem lab. Tests showed that the stone had a spectroscopic spectrum consistent with ruby. But it also displayed a moderately prominent orange-to-blue flash effect, small clusters of whitish devitrification products, and flattened gas bubbles, which are indicators of lead glass. Subsequent testing backed this assertion.


Photos courtesy of GIA

“Lead glass–filled ruby has been in the market for several years, and flame-fusion synthetic ruby for much longer, but this was the first example of a lead glass–filled flame-fusion synthetic ruby seen in the Carlsbad laboratory,” said the item authored by staff gemologist Nathan Renfro. “It is unclear why anyone would knowingly produce this gem material, which represents a new low in the realm of lead glass filling.”

As with lead glass-filled natural rubies, industry experts say this discovery demonstrates that ruby buyers must be on alert.

“It is another thing that people have to look out for, especially in the mass market where people don’t check every stone,” says Russell Shor, GIA senior industry analyst. “This was a big stone, so somebody sent it in. But a lot of low level items never go through labs.”