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Zhang J.,National Gems and Jewellery Technology Administrative Center | Lu T.,National Gems and Jewellery Technology Administrative Center | Chen H.,National Gems and Jewellery Technology Administrative Center
Gems and Gemology | Year: 2013

Ten coated jadeite jade samples were investigated by standard gemological testing, DiamondView imaging, confocal laser scanning microscopy, and spectrophotometry, including visible-range, FTIR, and Raman. The light green coating's Mohs hardness and refractive index were much lower than that of uncoated jadeite. Portions of the coating had peeled off in some cases, exposing the true color of the jadeite below. Measurements using a confocal scanning microscope indicated an average coating thickness of about 16 ìm. Diamond- View observations revealed a difference in fluorescence reaction between the surface coating and the jadeite beneath it. Visible-range spectroscopy showed a weaker broad band at approximately 630 nm and a moderate peak at 437 nm, without the approximately 691 nm band found in untreated jadeite containing chromium. The coated samples' FTIR spectra contained four characteristic bands at about 2856, 2873, 2928, and 2958 cm-1, while the Raman spectra showed a broad band near 2000 cm-1. These results indicated the presence of an organic polymer in the coating material. © 2013 Gemological Institute of America. Source


Zhang J.,National Gems and Jewellery Technology Administrative Center | Lu T.,National Gems and Jewellery Technology Administrative Center | Wang M.,National Gems and Jewellery Technology Administrative Center | Chen H.,National Gems and Jewellery Technology Administrative Center
Gems and Gemology | Year: 2011

A systematic study of 15 neutron-irradiated blue topaz samples was conducted using high-purity germanium (HPGe) digital gamma-ray spectroscopy. The specific activity of the detected radionuclides ( 134Cs, 182Ta, 46Sc, and/or 160Tb) was measured, and the decay pattern of the irradiated topaz was determined. Based on the time elapsed since their removal from the nuclear reactor, the amount of time required for the residual radioactivity to decay to safe levels was calculated. Most of the samples were safe at the time of the first measurement (95 days after irradiation), but higher concentrations of radionuclide impurities in some samples will require them to be quarantined for several years. © 2011 Gemological Institute of America. Source

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