TECHNICAL EVOLUTION AND IDENTIFICATION OF RESIN-FILLED TURQUOISE.

Zhushan County is the most abundant source of commercial turquoise in China's Hubei Province, where mass production has been ongoing for several decades. Chinese turquoise production and consumption have created a significant industry and promoted local economic prosperity and development. Treatment techniques for turquoise have been updated and changed rapidly, sometimes even monthly. Traditionally, rough materials are treated with resin to reduce their high porosity to improve processability, appearance, and stability. In this research, the characteristics of resin-filled turquoise were investigated by ultraviolet fluorescence, spectrofluorometry, and Fouriertransform infrared spectrometry. The differences in three-dimensional fluorescence patterns between untreated and resin-filled turquoise are reported for the first time. The three-dimensional fluorescence patterns along with the ultraviolet reactions and infrared spectra allow for the identification of this filling. Unlike untreated turquoise, the resin-filled turquoise samples had a strong and main emission peak centered at approximately 444 nm and a secondary emission shoulder at approximately 460 nm under approximately 372 nm wavelength excitation in this research. This study sheds light on resin filling processes by observing the essential features of 342 turquoise specimens after treatment. Resin filling can decrease the porosity of turquoise to improve its color and its value, and this study provides identification guidelines for gemologists and useful information on the resin-filling process. [ABSTRACT FROM AUTHOR]