JIN Ying-fu
(Dept. of Product Design, Academy of Fine Arts, Yanbian University, Yanji 133002, China)
Abstract: Geuda is a sapphire, having little value as a gem stone due to its semitransparent milky appearance with enough Fe2O3 and TiO2 coloring element contents. We investigated the color and inclusion evolution with 1600℃-5 h and 1800℃-1 h vacuum heat treatment by wave dispersive X-ray fluorescence spectroscopy (WD-XRF), optical microscopy, UV-VIS-NIR spectroscopy, Fourier-transform infra-red spectroscopy, and micro-Raman spectroscopy. According to WD-XRF, it’s confirmed the presence of Fe2O3 and TiO2 contents in Geudas as much as those in synthetic blue sapphires. In addition, the X-ray irradiation led to surface color change into vivid yellow. Optical microscopy shows that dramatic color change into blue and inclusion area at 1800℃ heat treatment while no change occurs at 1600℃ heat treatment. Moreover, for samples treated at 1600℃, no change was observed by UV-VIS, FT-IR, and micro Raman characterization. However, for samples treated at 1800℃, 450 nm (blue) transmission increases and inclusion development is observed through UV-VIS measurement. We concluded that 1800℃ heat treatment would be favorable for color enhancement in Geudas.
Keywords: FT-IR; heat treatment; micro-Raman; sapphire; WD-XRF
ACTA MINERALOGICA SINICA Vol. 35, No. 4, 2015, Page 550-554
