“黑青”和“黑碧”的谱学鉴别特征初探

代路路; 杨明星

doi:10.15964/j.cnki.027jgg.2019.S1.016

“黑青”和“黑碧”的谱学鉴别特征初探

Spectral Identification Characteristic of Nearly Black Tremolite-Nephrite("Heiqing") and Actinolite-Nephrite("Heibi")

摘要

摘要: “黑青”指颜色近黑色、主要成分为透闪石的青玉，“黑碧”指颜色近黑色、主要成分为阳起石的碧玉。通过电子探针、激光剥蚀电感耦合等离子体质谱仪、X射线粉末衍射仪等测试方法对“黑青”和“黑碧”样品的化学成分和矿物种类进行区分研究。结果显示，“黑青”样品的w(FeO_T)=2.21%~2.98%，“黑碧”样品的w(FeO_T)=8.12%。拉曼光谱测试显示，“黑青”样品为标准的透闪石峰位，“黑碧”的主峰位有几个波数的偏差，向波数小的方向移动，原因可能是其Fe质量分数较大所致。显微紫外-可见分光光度计(透射法)测试出在400~800 nm范围内，“黑青”样品在450、680 nm处有吸收带，归属于Fe的作用。“黑碧”样品在450 nm处有吸收带，归属于Fe的作用，660和690 nm附近有宽的吸收带，归属于Cr³⁺的作用；显微紫外-可见分光光度计的近红外区域，“黑青”样品在1 397、1 915、2 120、2 130、2 388、2 465 nm处有吸收带，“黑碧”样品在1 400、2 313、1 394 nm处有吸收带。标准软玉的光谱在1 390~1 420 nm为OH+H₂O二者合成峰，1 915 nm附近强吸收峰以及附近的弱吸收峰为水分子弯曲振动与伸缩振动吸收峰组合频所致，2210~2 300 nm归属Fe-OH吸收作用，2 300~2 400 nm归属Mg-OH吸收作用。近红外光谱(透射法)的测试结果，“黑青”样品HQ-1在：5 224 cm^-1(1 915 nm)、4 738 cm^-1(2 120 nm)、4 349 cm^-1, 4 317 cm^-1(2 310 nm)、4 190 cm^-1(2 388 nm)、4 064 cm^-1(2 465 nm)处有吸收峰；“黑碧”样品MQ在4 708 cm^-1(2 124 nm)、4 308 cm^-1(2 313 nm)、4 178 cm^-1(2 394 nm)处有吸收峰，测试结果与显微紫外-可见分光光度计保持一致。

Abstract: "Heiqing" refers to dolomite-related nephrite with the colour of the nearly black, whose main mineral component is tremolite(tremolite-nephrite). "Heibi" refers to serpentinite-related nephrite with the colour of the nearly black, whose main mineral component is actinolite(actinolite-nephrite). In this paper, the chemical compositions and mineral components were tested by EPMA, LA-ICP-MS and XRD.The EPMA testing results show that the FeO_T content of "Heiqing" samples (2.21%-2.98%) is higher than that of "Heibi" samples (8.12%). Raman spectra show that the "Heiqing" samples reveal the standard tremolite absorption peaks, while the main peak positions of "Heibi" samples have several wavenumber deviations, moving in the direction of small wavenumber maybe caused by Fe content. According to the transmission test of micro-ultraviolet-visible spectrophotometer, it is found that there are absorption bands at 450, 680 nm of "Heiqing" samples at 400-800 nm, which attributed to the role of Fe. "Heibi" samples have 450 nm absorption bands and attributed to the role of Fe, and there are 660, 690 nm near a wide absorption band, which attributed to the role of Cr³⁺. The micro-ultraviolet-visible spectrophotometer testing results show "Heiqing" samples have absorption bands at 1 397, 1 915, 2 120, 2 130, 2 388, 2 465 nm, while "Heibi" samples have absorption bands at 1 400, 2 313, 1 394 nm. According to the literature, in nephrite the absorption of 1 390—1 420 nm is the synthesized peak of OH+H₂O, the strong absorption peak near 1 915 nm and the nearby weak absorption peak are the combined frequency of water molecule bending vibration and stretching vibration absorption peak, and 2 210—2 300 nm absorption attributed to the role of Fe-OH, 2 300—2 400 nm absorption attributed to the role of Mg-OH. The near-infrared spectroscopy transmission test results suggest that "Heiqing" samples have absorption peaks at : 5 224 cm^-1(1 915 nm), 4 738 cm^-1(2 120 nm), 4 349 cm^-1, 4317 cm^-1(2 310 nm), taking sample HQ-1 as an example."Heibi" samples have absorption peaks at 4 708 cm^-1(2 124 nm), 4 308 cm^-1(2 313 nm), 4 178 cm^-1(2 394 nm) taking sample No. MQ as an example. And the test results of near-infrared spectroscopy are consistent with the micro-ultraviolet-visible spectrophotometer.

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