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Yang L.,National Gemstone Testing Center | Zhang B.,National Gemstone Testing Center | Shen M.,National Gemstone Testing Center | Mu S.,Wuhan University of Technology
Journal Wuhan University of Technology, Materials Science Edition | Year: 2011

Optical and micro-infrared microscope were used to observe the internal structure and mineral composition of high and low quality Chinese seawater and freshwater cultured pearls. Results clearly reveal that aragonite and calcite are found in seawater cultured pearls, but vaterite is not found. In contrast, vaterite and aragonite are found in freshwater cultured pearls, but calcite is not found. Based on our analysis and observations of the internal structure of high and low quality cultured pearls, a modifi ed integrated model of the internal structure of Chinese cultured pearls was established. Our revisions to the previous model focus on signifi cant differences within the prismatic layer of Chinese cultured pearls. © Wuhan University of Technology and SpringerVerlag Berlin Heidelberg 2011.

Feng X.-Y.,National Gemstone Testing Center | Lu T.-J.,National Gems and Jewelry Technology Administrative Center | Zhang H.,Yunnan Land and Resources Vocational College | Zhang Y.,National Gems and Jewelry Technology Administrative Center | Zhang J.,National Gemstone Testing Center
Kuangwu Yanshi/ Journal of Mineralogy and Petrology | Year: 2015

Nephrites from Xinjiang, Qinghai, Taiwan and so on were studied by using Raman spectroscopic. Specifically, a variety of nephrite with different colors, such as Baiyu, Qingyu, Huangyu and Biyu were investigated over their cations at M] and M3 sites. Raman spectra in the fingerprint region showed that the main composition of nephrite is tremolite. The replacement of impurity ions leads to some nuances in the chemical composition for a variety of nephrite with different colors. The peak of M-OH stretching vibration is important for recognizing the main chemical composition of nephrite as well as its color categorization. Ratio of Mg2+/ (Mg2+ + Fe2+) were calculated by using peak intensity ratio of 3 675 cm-1 ,3 661 cm-1,3 645 cm-1 ,and the relative content of Fe,Mg element was tested by using X-ray fluorescence and electron probe. The reliability tested by using EDXRF and electron probe indicated that the method of peak intensity ratio of 3 675 cm-1,3 661 cm-1 ,3 645 cm-1 can be used as a reference for evaluating nephrite whiteness.

Yin K.,Wuhan University | Tian J.,Hubei University | Ma Y.-B.,National Gemstone Testing Center | Wu Y.,National Gemstone Testing Center | Wang Y.,Hubei University
Guang Pu Xue Yu Guang Pu Fen Xi/Spectroscopy and Spectral Analysis | Year: 2014

Mineralogy and coloration of oil-green jadeite jade were investigated using X-Ray diffraction (XRD), Fourier transform infrared absorption spectroscopy (FTIR) and scanning electron microscopy (SEM). XRD results show that “flesh” of oil-green jadeite jade is mainly composed of relatively pure jadeite, whereas the “skin” of which is dominated by jadeite, chlorite and chrysotile. The mineral constituents revealed by FTIR are fairly consistent with XRD. Three typical adsorption peaks of ~2 956, ~2 919 and ~2 850 cm-1 related to organic matters occurred in both “flesh” and “skin” of oil-green jadeite jade. Jadeite in “flesh” exhibits an obvious columnar growth and has a better crystallinity than that of “skin”. However, jadeite in “skin” is richer in magnesium than that of “flesh”, suggesting an intense water-rock reaction of jadeite in “skin”. Chrysotile just occurs in “skin” of oil-green jadeite jade, and it presents a curved crystal plane. Flaky chlorite was detected in both cracks of “flesh” and “skin”, which might be the main cause of coloration of oil-green jadeite jade. Chlorite, formed in the reducing water-rock reaction, would adsorb or wrap a certain amount of organic matters, resulting in the occurrence of the characteristic adsorptions of oil-green jadeite jade. ©, 2014, Science Press. All right reserved.

Han W.,Wuhan University | Hong H.-L.,Wuhan University | Wu Y.,National Gemstone Testing Center | Yin K.,Wuhan University
Guang Pu Xue Yu Guang Pu Fen Xi/Spectroscopy and Spectral Analysis | Year: 2013

In order to study the color-genetic mechanism of brown jade, samples collected from Xinjiang were studied using XRD, ICP-MS, Raman and HRTEM. The results are as follows: the main mineral composition of brown jade is tremolite. ICP-MS data show that the concentration of the brown color has a good relationship with Fe element, samples with deeper color have higher Fe content. Fe occurs as iron mineral distributed in the tremolite particles or the microcracks. The grain size of the muddy iron mineral is extremely small, and the content is low. Experiments were designed to enrich the iron mineral with Stokes law. Then we studied the enriched samples with TEM and got the electron diffraction patterns of iron mineral, and identified them to be goethite. We conclude that the brown coloration of nephrite is due to goethite distributed in the tremolite particles or the microcracks. Raman spectra show that the rare mineral particle at the surface of the sample is rutile, and because of the low content, rutile has a little influence of the coloration.

Li J.,Hubei University | Yin K.,Hubei University | Han W.,National Gemstone Testing Center | Hong H.,Hubei University
Journal of Computational and Theoretical Nanoscience | Year: 2016

The gemological conventional testing, Fourier Transform Infrared Spectroscopy (FTIS), X-ray spectrofluorimetry and scanning electron micrograph analysis were adopted to conduct a systematic research of regular characteristics, spectroscopic characteristics, chemical components and microstructure of the red opal. The gemological regular conventional testing results suggested that the infrared absorption characteristic of the red fire opal, the natural fire opal and the newlycombined fire opal were basically similar. The X-ray spectrofluorimetry showed that Fe and Cu might be the major coloring elements, which were evenly distributed in the fire opal in the microcrystalline form of the hematite (Fe2O3) and the cuprite red (Cu2O). The scanning electron micrograph analysis suggested that the red fire opal was made up of silicon dioxide (SiO2) balls of irregular shapes. The diameter of these SiO2 balls was only dozens of nm, thus being unable to diffract and intervene in the visible light. Consequently, the red fire opal cannot generate the chatoyance effect. All the above gemological conventional test results and the test results of the large-scale instruments suggested that the red fire opal adopted by this research was the natural fire opal. Copyright © 2016 American Scientific Publishers. All rights reserved.

Guo Y.,China University of Geosciences | Mo T.,National Gemstone Testing Center
2010 OSA-IEEE-COS Advances in Optoelectronics and Micro/Nano-Optics, AOM 2010 | Year: 2010

The optimal illuminant of jadeite-jades' color green were confirmed by the 277 pieces jadeite-jades' analysis of L*, C* and □E* 2000 under 3 standard illuminants D65, CWF, and AError! Reference source not found.. By the contrastive analysis of theoretical and tested spectral distribution between standard illuminant CWF and D65, A, it is revealed that D65 has continuous and smooth spectral distribution with high color temperature, combined with the testified little effects on jadeite-jades' lightness from illuminants changing by ANOVA, D 65 is the illuminant which benefits for C* and L* of jadeite-jades' color green most. Color difference analysis shows that co mpared with other two illuminants, the average □E*2000 is the biggest and sample variance is the smallest under illuminant CWF. It is concluded that the standard illuminant D65 and CWF are the best illumination source and evaluating source of jadeite jade color green respectively.

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