Study on the Spectrum and Visualization of “Trapiche” Tourmaline Based on Hyperspectral Imaging Technology
CHEN Cheng1, YAN Bing1, YIN Zuo-wei1*, CAO Wei-yu2, WANG Wen-jing1
1. Gemmological Institute, China University of Geosciences (Wuhan), Wuhan 430074, China
2. Tianjin Product Quality Inspection Technology Research Institute, National Testing Center for Gold and Silver Jewelry (Tianjin), Tianjin 300384, China
Abstract：“Trapiche” tourmaline is a rare variety of tourmaline. Conventional gemstone identification instruments, infrared spectrometers, X-ray fluorescence spectrometers, and hyperspectral imaging techniques were used to test and analyze it. This paper aims to discuss the application of hyperspectral imaging technology in complex samples and enrich the multi-angle study of “trapiche” tourmaline. There are abundant parallel tubes and black solid inclusions in “trapiche” tourmaline. The visual boundary difference is due to the multidirectional distribution of parallel tubular inclusions. The parallel tubular inclusions in region a of the hexagonal column are arranged almost perpendicular to the c-axis. In the r region, the tubular inclusions of the three rhomboid regions divided by the three black arms of “trapiche” radiate outward along the c axis at an angle of 10°～30°. The appearance of the “trapiche” phenomenon comes from the fact that the black inclusions extend from the middle to the outside in three directions, and many of them are attached to the outside or wrapped in the inside of the tubular inclusions. Using the hyperspectral imaging technique, the average reflectance spectral lines and visual images of the region of interest of “trapiche” tourmaline are obtained. The hyperspectral pattern is consistent with the shading of the selection, and a wide absorption band centered at 440 nm in the purple region and 610 nm in the orange-red region appears. The content of Cr and V is high in the combination component analysis. It is considered that the d—d electron transition of Cr3+ causes the green color, and the D-electron spin allowed the transition of V3+. The visualized image shows the test state of the sample along the direction of the c-axis, the edge hexagonal column a gradually disappears, and the central three-square single cone r gradually occupies the entire plane. The pixel ratio between the green zone and the whole plane ranges from 16.81% to 49.96%. The proportion of black arms on both sides of the slice is inconsistent, and the number of black inclusions at both ends of the crystal does not show a linear relationship, but along the +c-axis, the change rate increases. The advantage of hyperspectral imaging technology lies in its ability to rapidly identify and analyze the distribution and concentration of different components in “trapiche” tourmaline and provide detailed information on the mineral's internal structure and crystal orientation. Identifying microscopic inclusions in minerals is of significant importance for understanding the mineral's genesis processes and environmental conditions.
陈 程，闫 冰，尹作为，曹维宇，王文婧. 基于高光谱成像技术的“达碧兹”电气石光谱与可视化研究[J]. 光谱学与光谱分析, 2024, 44(12): 3429-3434.
CHEN Cheng, YAN Bing, YIN Zuo-wei, CAO Wei-yu, WANG Wen-jing. Study on the Spectrum and Visualization of “Trapiche” Tourmaline Based on Hyperspectral Imaging Technology. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2024, 44(12): 3429-3434.
