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  GIA scientists surprised to discover a lead-glass filled synthetic ruby

October 14, 2012

Lead-glass filled rubies have become standard fair in recent years, and have been a subject of numerous gem lab alerts and articles in the trade press. Consequently, while gemologists at the Gemological Institute of America were not surprised to see evidence of lead-glass filling in an 11.52-ct. ruby being examined, they were astounded to discover the ruby was synthetic.

News of the unusual discovery was made public in the GIA's September 11 eBrief. In the article, the organization reported that, while initial observations were quite standard, microscopic examination revealed details out of the ordinary.

The gem itself contained subtly curving striae, which identified it as flame-fusion synthetic ruby, and a network of uniformly patterned fractures was consistent with those often seen in quench-crackled corundum. But the fractures showed a moderately prominent orange-to-blue flash effect, as well as small clusters of whitish devitrification products and flattened gas bubbles. Those are indicators of lead glass-filled corundum.

EDXRF spectroscopy then confirmed the presence of lead.

"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," wrote GIA's 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," he added.

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