Lead-Rich Glass Substance in Filled Treated Rubies

QI LI-jian (1), C. G. Zeng (2), YUAN Xin-qiang (1)
(1) Gemmological Institute, China University of Geosciences, Wuhan 430074, China ;
(2) Nan Yang Gemological Institute, Singapore

Abstract: The latest developed lead-rich glass-filled rubies, which have recently appeared on gem markets, are researched. By using routine analysis in corporation with the advanced lab analysis technique such as EPMA, UV-VIS and LRS, the chemical compositions, crystal phase, space distribution, and microstructure as well as spectrum characteristics of secondary glass in such treated rubies are investigated in depth. The results show that the main chemical composition of the glass filler is w (PbO) (74% ~ 75%), followed by w (AL2O3) (13% ~14%) and w (SiO2) (11% ~ 12%), and the crystallization is poor. In addition, there are some crystal inclusions such as rutile and apatite that are not altered or dissolved during the treatment, and this has normally been seen in unheated corundum. All these features are quite different from the traditional rubies which are treated by aluminium silicate glass, phosphorus aluminium glass and boron natrium-aluminium glass. Blue to bluish green flash effect, residual flat gas bubbles, UV-VIS, LRS, EPMA backscattered electron image and secondary electron image usually give enough evidence for detection of this latest treatment. The analysis results show that the fissures and cracks in rubies are filled with lead-rich glass at medium temperature.

Keywords: ruby; lead-rich glass; filling treatment

*Published in Journal of Gems and Gemmology, 2005, Vol 7, No.2, page 1 - 6.