白-黄色系绿松石“伴生矿”的红外光谱表征及其意义

doi:10.3964/j.issn.1000-0593(2018)10-3084-06

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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

Received: 2017-10-09 Accepted: 2018-03-03

ZTFLH:

P575

Corresponding Authors: LIU Xian-yu E-mail: 17105@gench.edu.cn

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https://www.gpxygpfx.com/EN/10.3964/j.issn.1000-0593(2018)10-3084-06 OR https://www.gpxygpfx.com/EN/Y2018/V38/I10/3084