SONG Yan-jun1,2, ZHANG Yi-cheng3, WU Yun-long3, Zhang Lu4
(1. College of Gemological and Material Techniques，Hebei GEO University, Shijiazhuang 050000, China;
2. Earth Science and Resources College of Chang’an University，Xi’an 710000, China;
3. National Testing Center for Gold and Silver Jewelry，Tianjin 300000, China;
4. Institute of Prospecting Technology，Langfang 065000,China)
Abstract: Spectral characteristics and coloration mechanism of silver-gray seawater cultured pearls produced by Pinctada fucata martensii were studied by Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, Ultraviolet–visible spectroscopy reflectance spectrometry (UV-VIS) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). White color seawater cultured pearls samples have also been tested as reference. FTIR and Raman spectra reveal that the main mineral component of the silver-gray color seawater cultured pearls is aragonite and no characteristic peaks caused by organic pigment obtained，but mean value of 876 cm-1 which caused by v2 vibration is higher than natural inorganic aragonite obviously in FTIR spectroscopy. UV-VIS spectra indicate that white seawater pearls have no absorption in visible region when silver-blue-gray color pearls have the absorption region at 475－555 nm. LA-ICP-MS results show that the contents of Mg and Mn in silver-gray color samples are higher than those in white samples which may be the main cause of coloration of silver-gray pearls.
Keywords: Seawater pearl; coloration mechanism; spectral characteristics; Pinctada martensii
E-mail: gemologist@foxmai.com
ACTA MINERALOGICA SINICA Vol. 37, No. 6, 2017, Page 712-716
