gems, corundum, treatments.6

The association of ruby with treatments that result in an addition of glass to the final product began in 1984 with the appearance on the market of Thai origin rubies in which cavities had been filled with glass (Kane, 1984, Scarratt, et al., 1984) a treatment that had evolved into glass crack filling by 1987 (Hughes, 1987, Scarratt, 1987). In 1992 with the discovery of corundum deposits in the area of Mong Hsu, Burma (Myanmar) that required high temperature-flux heating regimes to bring the material to market the association of ruby treatments and glass was dramatically expanded (Hlaing, 1993, Kremkow, 1993, Laughter, 1993, Peretti, 1993, Smith, et al., 1994). Twenty years after the first association a new ruby-glass association a new form of glass fracture filling in ruby appeared on the market (GAAJ, 2004, Pardieu, 2005, Smith C.P., 2005, McClure, 2006). Pardieu (Pardieu, 2005) noted that “some terminology problems may occur about this treatment regarding to the “Lead Glass” definition as many different formulas can be used: Pure lead oxide, lead oxides mixed with silica or fluxes like borax can be encountered... Temperatures, parameters and result can be very different. Some specific studies will probably be done in the future regarding to this issue”. Pardieu (Pardieu, 2005) also witnessed the treatment procedure as performed in Chantaburi, Thailand by Master Burner Mahiton Thondisuk and reported that “the most suitable rubies for repair are stones with color potential and that are rich in fissures”. He stated further that “this new treatment is performed currently mostly on Andilamena rubies (Madagascar) on which Mr. Thondisuk has had extensive experience but any ruby material with fissures could be “repaired”. It is a multi step treatment involving simple heating and the use of different lead rich compounds to fill the fissures and cavities of the stones. If most of the “repaired” stones seen were large size stones, stones less than 1 carat have also been treated this way”. While Pardieu did allude to wide tracts of glass crossing the surface of examples he examined in 2004 – 5 until recently (early 2008) the material observed in laboratories1 had an equivalence to treatments applied to “clarity enhance” emeralds (with the use of resins and oils) and diamonds (glass) and therefore the terminology used was adapted from these, i.e., minor, moderate or significant clarity enhancement. In reality the vast majority fell into the significant clarity enhancement category although as McClure (McClure, 2006) points out “ the efficiency of the treatment is such that a single large fracture in an otherwise clean ruby could be made to “disappear” to the unaided eye exactly as filled fractures can be made to “disappear” in emeralds and diamonds. In fact, we have already seen several stones that fall into this category. Further and following stability tests laboratories within the Laboratory Manual Harmonization Committee (LMHC)2 added “Glass filler may be unstable to elevated temperatures and to chemical agents. Special care shall be taken when repairing jewelry items set with glass filled corundum. During jewelry repair the unmounting of such stones is recommended” to reports on these stones. During a meeting of the LMHC held October 18th -20th 2007 in New York City, 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 being submitted to their laboratories and that in many cases the glass was filling wide seams crossing facets and seemed to be accounting for an ever increasing volume of the finished product. Further, it was surmised from observation that the material was being held together by the glass, i.e. the glass acting in similar manner to an adhesive. Following discussions and an agreement that this treatment went beyond what might be regarded as a “fracture filling or clarity enhancement process”, the group decided to describe this (heavily treated) material as “ruby-glass composites” i on all future identification reports. Further on November 13th 2007 American Gem Laboratories (AGL) announced that they were changing their reporting policies with regards these stones (AGL, 2007) and indicated that their report wording henceforth would be Identification: Composite Ruby, Standard enhancement: Heat, and Additional enhancement: Lead-glass. They also indicated a further comment would be added -This ruby has been heavily treated using a high refractive index lead-glass to fill fractures and cavities,vastly improving the apparent clarity and potentially adding weight. The glass may be damaged by a variety of solvents. This paper describes several “rubies” treated with glass and experiments carried out at GIA Laboratory (Bangkok) and at GIA New York that demonstrate the LMHC assumption – that the stones are being ‘bonded together’ by glass. As an implication of these experiments and given that several gemstones (ruby, emerald and diamond being the most often cited but others including tourmaline and quartz being not uncommon) are “clarity enhanced” through the infusion of fractures with oils, resins and glass, the paper also introduces new (February 2008) nomenclature for describing stones that have been clarity enhanced and those that are clearly composites.