Earth Science Frontiers ›› 2023, Vol. 30 ›› Issue (2): 401-414.DOI: 10.13745/j.esf.sf.2021.11.9

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Growth heterogeneity and zonation characteristics of emeralds from Davdar, Xinjiang

CUI Di1,2,3(), WU Qiong4, LIAO Zongting1,2,3,*(), QI Lijian1,2,3, ZHOU Zhengyu1,2,3, ZHANG Lingmin1, ZHONG Qian5, LIU Yiceng1,2,3, LI Ling1,2,3   

  1. 1. School of Ocean and Earth Sciences, Tongji University, Shanghai 200092, China
    2. Laboratory of Gem and Technological Materials, Tongji University, Shanghai 200092, China
    3. Shanghai Engineering and Technology Research Center of Gem and Material Technology, Shanghai 200092, China
    4. Guizhou Education University, Guiyang 550018, China
    5. Hubei Relics Archaeology Institute, Wuhan 430077, China
  • Received:2021-03-02 Revised:2021-09-14 Online:2023-03-25 Published:2023-01-05
  • Contact: LIAO Zongting


The chemical composition, microstructure and element-mapping characteristics of the color-zoned emeralds from Davdar, Xinjiang are investigated using gem microscope, polarized microscope, electron microprobe (EPMA) and X-ray diffraction techniques. The microstructure reveals reliable evidence of periodic growth, which shows the emerald core is fragmented and corroded and the rim is relatively complete. X-ray diffraction data indicate that the Davdar emeralds can be assigned to “octahedral” beryl, with Al substitutions mainly by mafic ions, and alkali ions, mainly Na+, occupying the beryl channels for charge compensation. Chemical composition analysis shows the alkali metal contents decrease from the core to the rim in both new and old mine samples. The alkalinity of new mine samples is low (alkali metal <1%), while old mine samples have medium or high alkalinities (alkali metal between 1%-2% or > 2%). The growth zoning types include multiple-color or colorless core-green rim types, and Cr and V are the dominant coloring elements; and chemical heterogeneity of the growth microzones reflects the variable contributions from coloring ions and alkali and mafic ions.

Key words: Emeralds from Davdar, X-ray diffractometer, EPMA, zonation character, heterogeneity

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