内蒙古角力格泰地区碧玺的宝石学特征

Characteristic of Tourmaline from Jiaoligetai Area, Inner Mongolia

  • 摘要: 利用偏光显微镜、电子探针、紫外-可见光谱、红外光谱和拉曼光谱等测试方法对内蒙古角力格泰产地的碧玺样品进行深入的宝石学特征研究。研究结果表明,内蒙古碧玺样品的折射率为1.615~1.650,双折射率为0.015~0.020、相对密度为3.050~3.158,不同颜色内蒙古碧玺样品的折射率、双折射率和相对密度存在差异。偏光显微镜下,内蒙古角力格泰碧玺晶体中含有大量的裂隙,液相、气液两相流体包裹体和固体包裹体。其中,流体包裹体主要呈现不规则几何状和针管状。拉曼光谱显示,流体包裹体主要为含水和含碳物质,固体包裹体中含有铁和镁的氧化物。电子探针显示,内蒙古角力格泰碧玺样品中具有较大的Fe含量差异,含量在2.199%~13.998%,较国外其他产地碧玺的高,可作为产地的鉴定指标。紫外-可见光谱显示,主要吸光区在红区和蓝紫区,主波长相近。其中720 nm处的吸收窄带与Fe2+-Fe3+电荷转移有关,部分样品在415 nm上的窄带可能主要为Mn2+d-d电子跃迁所致。内蒙古角力格泰碧玺样品的红外光谱具有典型的碧玺特征,3 452~3 567 cm-1处为的O-H伸缩振动所致,1 397、1 340、1 391、1 332、1 273 cm-1等为B-O的伸缩振动谱带,以及在10 93、1 037、798、719 cm-1处与Si-O-Si和O-Si-O有关的吸收。本文首次综合全面地报道了内蒙古角力格泰地区碧玺的宝石学特征,为新的碧玺矿产资源提供了宝石学基础资料,同时也可为将来碧玺产地溯源提供基础材料。

     

    Abstract: By using polarizing microscope, electron probe, ultraviolet-visible spectrometer, infrared spectroscopy and Raman spectroscopy, the gemmological characteristics of tourmaline from Jiaoligetai area, Inner Mongolia were studied. The conventional testing results show that the refractive index of the tourmaline from Inner Mongolia is between 1.615-1.650, the birefringence is between 0.015-0.020, and the relative density is 3.050-3.158. The refractive index, birefringence and relative density vary with the colour of samples. Under the polarizing microscope, it was found that tourmaline samples from Inner Mongolia contain a large number of fissure, liquid phase inclusion, gas liquid two-phase fluid inclusion and solid inclusion. The fluid inclusion mainly presents in irregular geometry and needle tube. Raman spectra show that the fluid inclusion is mainly water-containing and carbon-contaishow inclusions. Solid inclusion contains oxides of iron and magnesium. EPMA shows Fe content of samples ranges from 2.199% to 13.998%, which is higher than that from the other foreign origins, which can be used as an identification index of the origin. The UV-Vis spectra show that the main absorption areas are in the red and blue-purple regions, with similar main wavelengths. The narrow absorption band at 720 nm is related to Fe2+—Fe3+ charge transfer pairs, and absorption at 415 nm of some samples may be mainly caused by Mn2+ d electron transition. The infrared spectra of samples have typical tourmaline characteristics. The absobelong peak at 3 452-3 567 cm-1 belongs to stretching vibration of O-H. absorption peaks at 1 397, 1 340, 1 391, 1 332, 1 273 cm-1 belong to B-O, and absorption peaks at 1 093, 1 037, 798, 719 cm-1 are related to Si-O-Si and O-Si-O. This paper comprehensively reports the gemmological characteristics of tourmaline from Jiaoligetai area, Inner Mongolia for the first time, which provides gemmological basic data for new tourmaline mineral resources and basic materials for the origin of tourmaline in the future study.

     

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