坦桑尼亚绿碧玺的矿物学特征及颜色成因

不同产地绿碧玺的产出特征、化学成分、致色机理和形成条件都存在差异.目前关于坦桑尼亚绿碧玺的矿物种属及颜色成因等问题还未得到解决,对其科学鉴定和品质评级造成了一定影响.本文采用红外光谱、拉曼光谱、电子探针、紫外可见光谱等测试技术,对坦桑尼亚绿碧玺宝石矿物学特征及颜色成因进行探究.结果表明:坦桑尼亚绿碧玺呈单晶体产出,无解...

Mineralogy Characteristics and Coloration Mechanism of Green Tourmaline in Tanzania

BACKGROUND: There are differences in the production characteristics, chemical composition, coloration mechanism and formation conditions of green tourmaline from different producing areas. At present, the mineral species and coloration mechanism of Tanzanian green tourmaline have not been solved, which makes it difficult for its scientific identification and quality rating.OBJECTIVES: To study the mineralogical characteristics and coloration mechanism of Tanzanian green tourmaline.METHODS: The mineral component was analyzed by infrared spectroscopy and Raman spectroscopy. Microtexture was characterized by polarized light microscopy. Electron probe microanalyzer, and ultraviolet-visible (UV-Vis) spectroscopy were applied to analyze the chemical composition.RESULTS: The main mineral component of tourmaline in Tanzania was MgO tourmaline, which was characterized by single crystal, small grain, no cleavage, and split development, and can be used as a gemstone. The main chemical component of green tourmaline was SiO₂, Al₂O₃, MgO and B₂O₃, with average contents of 37.52%, 36.26%, 9.65% and 8.42%, respectively. In addition, it contained a small amount of FeO, Cr₂O₃ and TiO₂. Combined with the absorption spectrum in the ultraviolet region of 440nm, 600nm and 680nm in UV-Vis spectroscopy, it was concluded that the tiny amounts of Cr³⁺ replacing Al³⁺ into the crystal lattice was the main cause of the green color.CONCLUSIONS: The mineralogical characteristics and coloration mechanism of green tourmaline in Tanzania was confirmed, which provides a theoretical basis for the scientific identification, further quality evaluation and utilization.