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MIAO Xu,SHI Miao,WANG Li-sheng.Mineral Composition and Genesis of Black Quartzite Jade from Linwu County, Hunan Province[J].Rock and Mineral Analysis,2021,(4):522-531
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Mineral Composition and Genesis of Black Quartzite Jade from Linwu County, Hunan Province
Received:December 03, 2020  Revised:June 18, 2021
DOI:10.15898/j.cnki.11-2131/td.202012030155
Key words: quartzite jade  mineral composition  mineralization  polarizing microscope  X-ray powder diffraction  X-ray fluorescence spectrometry  inductively coupled plasma-mass spectrometry
Author NameAffiliationE-mail
MIAO Xu School of Gemmology and Materials Science, Hebei GEO University, Shijiazhuang 050031, China
Key Laboratory of Strategic Key Mineral Resources in Hebei Province, Shijiazhuang 050031, China 
 
SHI Miao School of Gemmology and Materials Science, Hebei GEO University, Shijiazhuang 050031, China
Key Laboratory of Strategic Key Mineral Resources in Hebei Province, Shijiazhuang 050031, China 
miaoer727@126.com 
WANG Li-sheng School of Gemmology and Materials Science, Hebei GEO University, Shijiazhuang 050031, China  
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Abstract:
      BACKGROUND: Black quartzite jade is a type of commonly and commercially available jade. Many areas produce this gem.
OBJECTIVES: To analyze the gemological characteristics and mineral composition of the jade samples and to discuss their genesis.
METHODS: Conventional gemological tests, infrared spectrum tests, polarizing microscopy, X-ray powder diffraction analysis, X-ray fluorescence spectrometry, and inductively coupled plasma mass spectrometry were used.
RESULTS: Black quartzite jade from the Linwu County, Hunan Province, showed a medium-fine grain texture. The polarizing microscopy results revealed many crytalloblastic or palimpsest textures. The content of the main mineral quartz was 44.7%, the content of secondary minerals (mica and feldspar) was 31.0%, and the content of clay minerals was 12.7%. Minor organic carbon, iron minerals, andalusite, almandine, and pyrite were also observed.
CONCLUSIONS: Based on the main textures, structures, configuration features, and chemical compositions, the studied samples are regarded as typical low-to-moderate temperature hydrothermal regional metamorphic rocks, which are classified as greenschist facies. The source rock was composed of sedimentary rocks abundant with aluminum, quartz, and feldspar. The tectonic environment for its formation belonged to the continental margin. This study provides technical support for the identification of the mineral composition of quartzite jades from the Linwu County, Hunan Province.