A Study on IR Absorption Spectroscopy and XRD Characteristics of White and Yellow Natural Turquoise Associated Minerals
CHEN Quan-li1, LIU Xian-yu1, 2*, JIN Wen-jing1, ZHU Wen-jing1
1. Gemology Institute, China University of Geosciences, Wuhan 430074, China
2. School of Gemology, Shanghai Jian Qiao University, Shanghai 201306, China
Abstract：Recently there have been many natural minerals which are similar to turquoise in the market, commonly known as “turquoise associated minerals”, and are sold for business as a natural turquoise. These natural turquoise associated minerals are similar to natural turquoises in appearance while there are some difficulties in its identification. In this paper, the natural turquoise associated minerals of white and yellow varieties are selected, and their gemological characteristics and mineral composition are analyzed and studied by conventional gemological test, infrared absorption spectroscopy and X-ray powder diffraction. The results show that white and yellow natural turquoise associated minerals show earthy luster-weak glassy luster in different degrees. They are opaque and show relatively loose structure. The refractive index of the white sample is about 1.51 and the relative density is 1.86~2.28. The refractive index of the yellow sample is about 1.57~1.60 and the relative density is 2.32~2.72. The mineral compositions of white and yellow natural turquoise associated minerals are complex, and different even in the same color samples. The test of the spectrum by infrared absorption spectrum cannot effectively indicate the specific mineral composition, while the X-ray powder is the effective means to study the mineral composition of natural turquoise associated minerals. X-ray powder diffraction test results show that the main minerals of the white sample are phosphorus alum and phosphorus calcium alum; and the main mineral of the yellow sample is sodium alunite. The infrared absorption spectra of white and yellow samples show that the groups of SO4/PO4 had different vibrations, peak shapes and peak positions. According to the main mineral composition characteristics，the classification of infrared absorption spectrum for different samples can be fast and effective for its non-destructive identification.
Key words：Turquoise；Associated minerals；Infrared absorption spectrum X-ray powder diffraction mineral composition
陈全莉，刘衔宇，金文靖，朱文静. 白-黄色系绿松石“伴生矿”的红外光谱表征及其意义[J]. 光谱学与光谱分析, 2018, 38(10): 3084-3089.
CHEN Quan-li, LIU Xian-yu, JIN Wen-jing, ZHU Wen-jing. A Study on IR Absorption Spectroscopy and XRD Characteristics of White and Yellow Natural Turquoise Associated Minerals. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2018, 38(10): 3084-3089.
[1] CHEN Quan-li, QI Li-jian, ZHANG Yan(陈全莉，亓利剑，张 琰). Journal of Gems & Gemmology(宝石和宝石学杂志)，2006, 8(1): 9.
[2] LI Shu, DI Jing-ru, WANG Xiao-juan, et al(李 舒，狄敬如，王笑娟，等). Spectroscopy and Spectral Analysis(光谱学与光谱分析)，2016, 36(9): 2978.
[3] SHI Zhen-rong(石振荣). Geological of Jiangsu(江苏地质)，2008, 32(2): 109.
[4] SHI Zhen-rong, CAI Ke-qin, GONG Ming-quan(石振荣，蔡克勤，龚明权). Geological of Northwest(西北地质)，2008, 41(2)：56.
[5] SHI Zhen-rong, CAI Ke-qin(石振荣，蔡克勤). Acta Petrologica et Mineralogica(岩石矿物学杂志)，2008, 27(2): 164.
[6] SHI Zhen-rong, CAI Ke-qin(石振荣，蔡克勤). Superhard Material Engineering(超硬材料工程)，2007, 19(4): 56.
[7] Farmer V C(法默 V C，著). Translated by YING Yu-pu, WANG Shou-song, LI Chun-geng, et al(应育浦, 汪寿松, 李春庚，等译). Infrared Spectroscopy of Mineral(矿物的红外光谱). Beijing: Science Press(北京: 科学出版社), 1982 .
