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Spectral Characteristics and Coloration Mechanism of Silver-gray Color Seawater Cultured Pearls Produced by Pinctada Martensii (Vol. 37, No. 6, 2017) TEXT SIZE: A A A

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

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ACTA MINERALOGICA SINICA Vol. 37, No. 6, 2017, Page 712-716

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