NOTES & NEW TECHNIQUES ORIGIN DETERMINATION OF DOLOMITE-RELATED WHITE NEPHRITE THROUGH ITERATIVE-BINARY LINEAR DISCRIMINANT ANALYSIS Zemin Luo, MingxingYang, and Andy H. Shen Provenance studies on nephrite jade are of gemo- logical as well as archeological importance. Ori- gin determination is difficult to achieve relying solely on typical gemological properties and ob- servations. In this study, the authors present a new statistical analysis method, based on linear dis- criminant analysis (LDA) and trace-element data from laser ablation–inductively coupled plasma– mass spectrometry (LA-ICP-MS), to achieve sig- nificantly improved origin determination (an average of 94.4% accuracy) for eight major dolomite-related nephrite deposits in eastern Asia. As the principle is to compare one location to the rest in one round and continue such binary com- parison until all possible localities are tested, the method is referred to as iterative-binary LDA (IB- LDA). Combined with trace-element composition data from LA-ICP-MS, it could prove to be a use- ful technique for the geographic origin determi- nation of other gemstones. N ephrite jade has been of great interest to East Asian cultures dating back to the Neolithic Age (Wen and Jing, 1996; Tsien et al., 1996; Wen, 2001; Har- low and Sorensen, 2005). Historically, it has been con- sidered a symbol of wealth and power for Chinese emperors and nobility (figures 1A and 1B). Nephrite from countries such as China, Russia, and South Korea (Ling et al., 2013) continues to attract considerable at- tention as a gem and ornamental material, particularly in the Chinese market. Thus, geographic origin deter- mination is important in terms of proper classification, valuation, and archaeological implications. See end of article for About the Authors and Acknowledgments. GEMS & GEMOLOGY , Vol. 51, No. 3, pp. 300–311, http://dx.doi.org/10.5741/GEMS.51.3.300. © 2015 Gemological Institute of America In Chinese culture, white is usually regarded as the color of purity and perfection (He, 2009). Due to its quality and well-established historical reputation, white nephrite from Xinjiang has maintained the highest price in the Chinese market. Xinjiang nephrite is usually translucent, with colors ranging from white and greenish white to yellow. The best material from this province is white nephrite with greasy luster, known in the trade as “mutton fat” jade. The purity, fine texture, and luster of white nephrite from Xinjiang come together to create an elegant cultural symbol (figure 1C). White nephrite from other deposits, including Baikal (Russia), Chuncheon (South Korea), and Qing- hai (China), has similar characteristics and is difficult In Brief • There is no universally accepted method to determine the origin of East Asian dolomite-related nephrite. • IB-LDA, a statistical analysis method developed by the authors, uses an algorithm based on trace-element data to determine the origin of nephrite from eight major production areas in China, Russia, and South Korea. • This method yielded greater accuracy than the tradi- tional LDA method, and may be useful for determining the origins of other gem materials. to distinguish with the unaided eye or even micro- scopic observation (Wu et al., 2002; Ling et al., 2013). In some cases, material from other locations has been falsely represented as Xinjiang nephrite jade to fetch higher prices. A reliable quantitative method for ge- ographic origin determination is urgently needed to protect nephrite consumers. Nephrite is a gem-quality tremolite or actinolite polycrystalline aggregate. It is usually classified as ei- ther dolomite-related or serpentine-associated, which 300 NOTES & NEW TECHNIQUES GEMS & GEMOLOGY FALL 2015