REN Huizhen, LI Liping. Chemistry of Opal from Ethiopia[J]. Journal of Gems & Gemmology, 2015, 17(4): 23-28.
Citation: REN Huizhen, LI Liping. Chemistry of Opal from Ethiopia[J]. Journal of Gems & Gemmology, 2015, 17(4): 23-28.

Chemistry of Opal from Ethiopia

More Information
  • Received Date: March 29, 2015
  • In 2008, a new opal deposit was discovered near Welo Province, Ethiopia. The opals from Ethiopia found in volcanic rocks with vivid play-of-colour are very different from those opals from other localities. LIBS, XRF, FTIR and TG—DSC were used to study the chemical composition and the water speciation in opal from Ethiopia. Comparing with opals from Australia and Mexico, research indicates that the concentrations of Ca, Sr and Ba in opal from Ethiopia are higher than those from other localities, which can be used as an indicator of opal from Ethiopia. The infrared spectrum of opal from Ethiopia shows a peak at 791 cm-1. It indicates that opal from Ethiopia is not completely amorphous. This feature is the same as Mexican opal with the similar geological origin, and is different from Australian opal with epigenetic origin. Opal from Ethiopia, Australia and Mexica show the same TG-DSC testing result, and two obvious endothermic valleys (80-100 ℃ and 200-600 ℃) indicate the loss of absorbed water and crystal water and structurally bounded respectively. The content and these two types of water show no difference in opals from all three localities.
  • [1]
    Rondeau B, Fritsch E, Mazzero F, et al. Play-of-colour opal from Wegel Tena, Wollo Province, Ethiopia[J]. Gems & Gemology, 2010, 46(2): 90-105.
    [2]
    Rondeau B, Cenki-Tok B, Fritsch E. Geochemical and petrological characterization of gem opals from Wegel Tena, Wollo, Ethiopia: Opal formation in an oligocene soil[J]. Geochemistry-Exploration Environment Analysis, 2012, 12(2):93-104.
    [3]
    Gaillou E, Delaunay A, RondeauB, et al. The geochemistry of gem opals as evidence of their origin[J]. Ore Geology Reviews, 2008, 34(1):113-126.
    [4]
    Adamo H, Ghisoli C, Caucia F. A contribution to the study of FTIR spectra of opals[J]. Neues Jahrbuch für Mineralogie-Abhandlungen, 2010, 187(1):63-68.
    [5]
    Brown L D, Ray A S, Thomas P S, et al. Thermal characteristics of Australian sedimentary opals[J]. Journal of Thermal Analysis & Calorim, 2002, 68(1):31-36.
  • Related Articles

    [1]LIU Xuegang, ZHAO Xiaobing, YANG Lixia, WEI Shani, DING Shan. Research on Virtual Restoration of Bronze Cultural Relic Halberd of King Guang of Wu Based on X-ray Detection and Photoshop Technologies[J]. Journal of Gems & Gemmology, 2024, 26(5): 59-68. DOI: 10.15964/j.cnki.027jgg.2024.05.007
    [2]GAO Jing, ZHANG Jinli, Yen Chien-Kuo. Synchrotron Radiation μ-XRF Imaging Reveals Oscillatory Zoning of Freshwater Pearls[J]. Journal of Gems & Gemmology, 2023, 25(1): 28-35. DOI: 10.15964/j.cnki.027jgg.2023.01.004
    [3]Longbo ZHANG, Bihan LIN, Qian ZHANG. Application of Synchrotron Radiation X-ray Fluorescence Spectroscopy in Gem Test:Take Agate from Alashan as Example[J]. Journal of Gems & Gemmology, 2020, 22(5): 23-30. DOI: 10.15964/j.cnki.027jgg.2020.05.003
    [4]SHENG Ke-ping. Application of Scanning Electron Microscope with Energy-Dispersive X-ray Spectrometer in Gem Identification[J]. Journal of Gems & Gemmology, 2010, 12(1): 32-35.
    [5]XU Zhi, WANG Huan-qin, LUO Yu-xin. Evaluation of Uncertainty in Gold Content Tested by X-ray Fluorescence Spectrometry[J]. Journal of Gems & Gemmology, 2009, 11(1): 39-41.
    [6]CHEN Shan, HUANG Yan-you, YANG Yan. Calibration Method of X-ray Fluorescence Spectrometer[J]. Journal of Gems & Gemmology, 2008, 10(4): 28-30.
    [7]WANG Bei, LU Ding-rong, WANG Xiao-xiao, WU Guo-jian. Method on Detecting Content of Platinum Jewelry by X-Ray Fluorescence Spectrometer[J]. Journal of Gems & Gemmology, 2007, 9(3): 11-14.
    [8]CHEN Tao, WU Xiang. Study on Synthetic Diamond with Laue Synchrotron Radiation Topography[J]. Journal of Gems & Gemmology, 2004, 6(1): 13-16.
    [9]QI Lijian, YUAN Xinqiang, TIAN Liangguang, YUAN Zhizhong. Evolution And Colouration of Lattice Defects in Diamonds at High Pressure and High Temperature[J]. Journal of Gems & Gemmology, 2001, 3(3): 1-7.
    [10]Tian Liangguang, Huang Wenhui, Cheng Youfa, Liu Huafeng, Tang Xin. GEMMOLOGICAL APPLICATIONS OF X-RAY DIFFRACTION TOPOGRAPHY TECHNIQUES[J]. Journal of Gems & Gemmology, 1999, 1(2): 41-44.

Catalog

    Article Metrics

    Article views (94) PDF downloads (23) Cited by()
    Related

    /

    DownLoad:  Full-Size Img  PowerPoint
    Return
    Return