corundum, treatments.6, inclusions.5, gems

Natural rubies are usually enhanced by heat treatment in a flux, and secondary glasses may be formed that then remain in the gems. These fluxes are commonly similar in appearance to glass inclusions found in flux-grown synthetic rubies. To differentiate between these two types of glasses, the chemical compositions and structural characteristics of both types were determined using electron microprobe and laser Raman microspectrometry (LRM) techniques.. Four types of glasses were found in the heat-treated natural rubies: sodic aluminosilicate glass, Na-P-Al glass, B-Na-Al glass, and aluminosilicate glass. Chemically, these glasses are significantly different from flux inclusions found in synthetic rubies. They differ not only in major elements, but also in trace elements. For example, Pb, W, Mo, and Bi present in synthetic rubies were not detectable in the glasses. The Raman spectra of the two materials also are distinct.TL