Color Origin of Greyish-Purple Tremolite Jade from Sanchahe in Qinghai Province, NW China
Greyish-purple tremolite jade has become well known in the past few years, and the origin of its color has attracted the attention of gemologists. In this study, FT-IR spectra, EPMA, EPR spectra, micro-XRF, UV–Vis–NIR spectra, and LA-ICP-MS in situ mapping were analyzed to investigate the chromophor...
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MDPI AG
2023-08-01
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| Series: | Minerals |
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| Online Access: | https://www.mdpi.com/2075-163X/13/8/1049 |
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| author | Nina Gong Chaowen Wang Shuai Xu |
| author_facet | Nina Gong Chaowen Wang Shuai Xu |
| author_sort | Nina Gong |
| collection | DOAJ |
| description | Greyish-purple tremolite jade has become well known in the past few years, and the origin of its color has attracted the attention of gemologists. In this study, FT-IR spectra, EPMA, EPR spectra, micro-XRF, UV–Vis–NIR spectra, and LA-ICP-MS in situ mapping were analyzed to investigate the chromophore elements. The study sample was chosen from the Sanchahe mine, Qinghai Province, NW China, which has the typical characteristics of a gradual color change. The FT-IR and EPMA results revealed that the mineral composition of the dark and light greyish-purple regions of the sample are primarily composed of tremolite. UV–Vis–NIR spectra demonstrated that the greyish-purple color is mainly due to strong absorptions at 560 nm and 700 nm and weak absorption at 745 nm in the visible range. The EPR spectra presented ~3400 G six hyperfine lines resulting from the hyperfine interactions of the unpaired electron with the Mn<sup>2+</sup> nucleus in the octahedral site. The UV–Vis–NIR and EPR spectra analyses demonstrated that Mn<sup>2+</sup> is the origin of the purple color. A comparison of the major elements in the light and dark regions indicated that the chromogenic elements have strong positive correlations with Mn, Cu, and Fe. LA-ICP-MS mapping used to analyze the first transition metals indicated possible positive correlations between the greyish-purple color and the trace chromogenic elements. This suggested that the Mn, Cu, and Fe contents are significantly high in the dark band region. Combining in situ LA-ICP-MS mapping of trace elements, UV–Vis spectra, and EPR analysis results, it was suggested that Mn, Cu, and Fe are the major contributors to the greyish-purple color. This study provides a reference for the specific experimental methods to determine chromophores and the origin of color in tremolite jades. |
| first_indexed | 2024-03-10T23:43:07Z |
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| language | English |
| last_indexed | 2024-03-10T23:43:07Z |
| publishDate | 2023-08-01 |
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| series | Minerals |
| spelling | doaj.art-df143732170744568aaa55679a589f2a2023-11-19T02:20:51ZengMDPI AGMinerals2075-163X2023-08-01138104910.3390/min13081049Color Origin of Greyish-Purple Tremolite Jade from Sanchahe in Qinghai Province, NW ChinaNina Gong0Chaowen Wang1Shuai Xu2Jewelry Institute, Guangzhou Panyu Polytechnic, Guangzhou 511487, ChinaGemmological Institute, China University of Geosciences, Wuhan 430074, ChinaSchool of Earth Sciences and Engineering, Sun Yat-sen University, Zhuhai 519080, ChinaGreyish-purple tremolite jade has become well known in the past few years, and the origin of its color has attracted the attention of gemologists. In this study, FT-IR spectra, EPMA, EPR spectra, micro-XRF, UV–Vis–NIR spectra, and LA-ICP-MS in situ mapping were analyzed to investigate the chromophore elements. The study sample was chosen from the Sanchahe mine, Qinghai Province, NW China, which has the typical characteristics of a gradual color change. The FT-IR and EPMA results revealed that the mineral composition of the dark and light greyish-purple regions of the sample are primarily composed of tremolite. UV–Vis–NIR spectra demonstrated that the greyish-purple color is mainly due to strong absorptions at 560 nm and 700 nm and weak absorption at 745 nm in the visible range. The EPR spectra presented ~3400 G six hyperfine lines resulting from the hyperfine interactions of the unpaired electron with the Mn<sup>2+</sup> nucleus in the octahedral site. The UV–Vis–NIR and EPR spectra analyses demonstrated that Mn<sup>2+</sup> is the origin of the purple color. A comparison of the major elements in the light and dark regions indicated that the chromogenic elements have strong positive correlations with Mn, Cu, and Fe. LA-ICP-MS mapping used to analyze the first transition metals indicated possible positive correlations between the greyish-purple color and the trace chromogenic elements. This suggested that the Mn, Cu, and Fe contents are significantly high in the dark band region. Combining in situ LA-ICP-MS mapping of trace elements, UV–Vis spectra, and EPR analysis results, it was suggested that Mn, Cu, and Fe are the major contributors to the greyish-purple color. This study provides a reference for the specific experimental methods to determine chromophores and the origin of color in tremolite jades.https://www.mdpi.com/2075-163X/13/8/1049greyish-purple tremolite jadenephritespectroscopic methodstrace elementMnFe |
| spellingShingle | Nina Gong Chaowen Wang Shuai Xu Color Origin of Greyish-Purple Tremolite Jade from Sanchahe in Qinghai Province, NW China Minerals greyish-purple tremolite jade nephrite spectroscopic methods trace element Mn Fe |
| title | Color Origin of Greyish-Purple Tremolite Jade from Sanchahe in Qinghai Province, NW China |
| title_full | Color Origin of Greyish-Purple Tremolite Jade from Sanchahe in Qinghai Province, NW China |
| title_fullStr | Color Origin of Greyish-Purple Tremolite Jade from Sanchahe in Qinghai Province, NW China |
| title_full_unstemmed | Color Origin of Greyish-Purple Tremolite Jade from Sanchahe in Qinghai Province, NW China |
| title_short | Color Origin of Greyish-Purple Tremolite Jade from Sanchahe in Qinghai Province, NW China |
| title_sort | color origin of greyish purple tremolite jade from sanchahe in qinghai province nw china |
| topic | greyish-purple tremolite jade nephrite spectroscopic methods trace element Mn Fe |
| url | https://www.mdpi.com/2075-163X/13/8/1049 |
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