Step 2: Advanced Gemology

Lesson 13

Leaded Glass Filled Ruby UPDATE, December 2016

Prior to 2006, most lead glass filled rubies contained only a very, very small percentage of glass in surface reaching fractures. Due to this small percentage, these stones qualified for the designation “treated rubies” by internationally respected gem labs.

However, treaters improved their ability to enhance ever lower grade material. As a result, the percentage of glass in the vast majority of the material on the market increased to the point it no longer qualified as a treated ruby. To protect consumers and the integrity of the trade, a new classification was necessary.

Ruby-Glass Composites vs. Treated Rubies

During a meeting of the Laboratory Manual Harmonization Committee (LMHC) in 2007, Dr. Pornsawat Wathanakul (Scientific Advisor to the GIT member) reopened discussions on glass fracture filling in ruby. Several members had noted myriads of large gas bubbles within the newer material submitted to their laboratories. In many cases, they found the glass filled wide seams crossing facets and accounted for an ever increasing volume of the finished product. Furthermore, members surmised from observation that the glass held the material together. In other words, the glass…