Mineralogy and Magnetic Behavior of Yellow to Red Xuanhua-Type Agate and Its Indication to the Forming Condition
Iron oxides/hydroxides are important magnetic minerals to provide information about changes in the forming environment. However, the magnetic behavior in agate has been rarely investigated. In this study, the magnetic behavior of the Xuanhua-type agate with intense yellow to red colors from the Xuan...
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MDPI AG
2021-08-01
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| Series: | Minerals |
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| Online Access: | https://www.mdpi.com/2075-163X/11/8/877 |
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| author | Danyi Zhou Guanghai Shi Suzhen Liu Bailing Wu |
| author_facet | Danyi Zhou Guanghai Shi Suzhen Liu Bailing Wu |
| author_sort | Danyi Zhou |
| collection | DOAJ |
| description | Iron oxides/hydroxides are important magnetic minerals to provide information about changes in the forming environment. However, the magnetic behavior in agate has been rarely investigated. In this study, the magnetic behavior of the Xuanhua-type agate with intense yellow to red colors from the Xuanhua District (China) was investigated by temperature dependence of magnetic susceptibility, hysteresis loop, isothermal remanent magnetization and the analysis of remanent coercivity components from the gradient acquisition plot. Yellow goethite and red hematite can be quantitatively identified by XRD and Raman spectroscopy due to their relatively higher content. Results showed that the red, yellow and orange Xuanhua-type agate had different magnetic behavior, and magnetite existed in the yellow and orange ones. Fluid inclusions in such agate had the homogenization temperature of ~168 °C to 264 °C. All results suggested that the dehydration of goethite to form hematite was the main reason for the high remnant coercivity (above 1000 mT) of hematite in the red agate. The co-existence of magnetite and goethite in the yellow and orange agate reflects the transformation from Fe<sup>2+</sup> to Fe<sup>3+</sup>, indicating the change in the redox property of the environment. Unique patterns mainly formed by hematite and goethite make it a popular gem-material with high research value. |
| first_indexed | 2024-03-10T08:34:07Z |
| format | Article |
| id | doaj.art-5b9b2e7788a9446fb2af88a534261707 |
| institution | Directory Open Access Journal |
| issn | 2075-163X |
| language | English |
| last_indexed | 2024-03-10T08:34:07Z |
| publishDate | 2021-08-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Minerals |
| spelling | doaj.art-5b9b2e7788a9446fb2af88a5342617072023-11-22T08:50:16ZengMDPI AGMinerals2075-163X2021-08-0111887710.3390/min11080877Mineralogy and Magnetic Behavior of Yellow to Red Xuanhua-Type Agate and Its Indication to the Forming ConditionDanyi Zhou0Guanghai Shi1Suzhen Liu2Bailing Wu3Beijing Institute of Gemology, National Gems & Jewelry Technology Administrative Center, Ministry of Natural Resources, Beijing 100013, ChinaState Key Laboratory of Geological Processes and Mineral Resource, China University of Geosciences, Beijing 100083, ChinaState Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, ChinaState Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, ChinaIron oxides/hydroxides are important magnetic minerals to provide information about changes in the forming environment. However, the magnetic behavior in agate has been rarely investigated. In this study, the magnetic behavior of the Xuanhua-type agate with intense yellow to red colors from the Xuanhua District (China) was investigated by temperature dependence of magnetic susceptibility, hysteresis loop, isothermal remanent magnetization and the analysis of remanent coercivity components from the gradient acquisition plot. Yellow goethite and red hematite can be quantitatively identified by XRD and Raman spectroscopy due to their relatively higher content. Results showed that the red, yellow and orange Xuanhua-type agate had different magnetic behavior, and magnetite existed in the yellow and orange ones. Fluid inclusions in such agate had the homogenization temperature of ~168 °C to 264 °C. All results suggested that the dehydration of goethite to form hematite was the main reason for the high remnant coercivity (above 1000 mT) of hematite in the red agate. The co-existence of magnetite and goethite in the yellow and orange agate reflects the transformation from Fe<sup>2+</sup> to Fe<sup>3+</sup>, indicating the change in the redox property of the environment. Unique patterns mainly formed by hematite and goethite make it a popular gem-material with high research value.https://www.mdpi.com/2075-163X/11/8/877magnetic behavioryellow goethitered hematiteXuanhuaagateformation |
| spellingShingle | Danyi Zhou Guanghai Shi Suzhen Liu Bailing Wu Mineralogy and Magnetic Behavior of Yellow to Red Xuanhua-Type Agate and Its Indication to the Forming Condition Minerals magnetic behavior yellow goethite red hematite Xuanhua agate formation |
| title | Mineralogy and Magnetic Behavior of Yellow to Red Xuanhua-Type Agate and Its Indication to the Forming Condition |
| title_full | Mineralogy and Magnetic Behavior of Yellow to Red Xuanhua-Type Agate and Its Indication to the Forming Condition |
| title_fullStr | Mineralogy and Magnetic Behavior of Yellow to Red Xuanhua-Type Agate and Its Indication to the Forming Condition |
| title_full_unstemmed | Mineralogy and Magnetic Behavior of Yellow to Red Xuanhua-Type Agate and Its Indication to the Forming Condition |
| title_short | Mineralogy and Magnetic Behavior of Yellow to Red Xuanhua-Type Agate and Its Indication to the Forming Condition |
| title_sort | mineralogy and magnetic behavior of yellow to red xuanhua type agate and its indication to the forming condition |
| topic | magnetic behavior yellow goethite red hematite Xuanhua agate formation |
| url | https://www.mdpi.com/2075-163X/11/8/877 |
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