Feature Gems & Gemology, Spring 2006, Volume 42, No. 1

Identification and Durability of Lead Glass–Filled Rubies

Shane F. McClure, Christopher P. Smith, Wuyi Wang, and Matthew Hall

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In early 2004, the GAAJ laboratory in Japan issued a lab alert about rubies they had seen that had large numbers of fractures filled with high-lead-content glass, which made them appear very transparent. Since then, large quantities of this material have reached international markets. This dramatic treatment is not difficult to identify with a standard gemological microscope, since it has characteristics similar to clarity-enhanced diamonds (flash effect, gas bubbles, etc.). However, locating filled cavities in reflected light is more challenging, as the surface luster of the filler is close to that of ruby. The filling material appears to be very effective in reducing the appearance of fractures. Durability testing of a few samples by highly skilled jewelers indicated that the filler was fairly resistant to heat exposure during jewelry repair procedures, but it reacted readily with solvents.