Laser & Optoelectronics Progress, Volume. 59, Issue 13, 1333001(2022)
Gemological Characteristics and Discoloration Mechanism of Color-Chang Pyrope-Spessartine Garnet
Garnet group belongs to nesosilicate minerals with A3B2[SiO4]3 as itsstandard chemical formula. Rarely, few garnets generate two distinct transmission windows due to the isotropic substitution of transition elements, such as Cr and V. This phenomenon leads to color-change as a variation of external light source, which produces purple-green and yellow-red colors under daylight and incandescent light, respectively. As the color-change effect is found in pyrope, spessartine, and pyrope-spessartine, we select the gem grade pyrope-spessartine in this study. Electron probe (EPMA), Fourier transform infrared (FT-IR) spectrometer, ultraviolet-visible (UV-Vis) spectrophotometer, and photoluminescence (PL) spectrometer were conducted on samples to understand the color-change mechanism. EPMA results showed that the samples could be defined as pyrope-spessartine, with few amounts of grossular and almandine. UV-Vis spectra showed that the tailing absorption band around 420 nm (belongs to d-d orbital transition of Mn2+, 6A1g→ 4Eg) overlay with a wide absorption band of 571 nm (belongs to d-d orbital transition of Cr3+,
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Xiaoxu Yan, Suwei Yue, Shiyu Chen. Gemological Characteristics and Discoloration Mechanism of Color-Chang Pyrope-Spessartine Garnet[J]. Laser & Optoelectronics Progress, 2022, 59(13): 1333001
Category: Vision, Color, and Visual Optics
Received: Jun. 17, 2021
Accepted: Aug. 10, 2021
Published Online: Jul. 1, 2022
The Author Email: Yue Suwei (yuesuwei@gcu.edu.cn)