From Gems & Gemology: Lead-Glass Filling in Colour-Change Sapphire
Gagan Choudhary of the Gem Testing Laboratory in Jaipur, India, submitted the following report to Gems & Gemology's (G&G) Gem News International section:
Lead-glass-filled rubies were first seen in the market in 2004. Much research has since been conducted to classify these rubies correctly, and the treatment is now well understood. We also know, though, that such fillings are now being applied to sapphires...