绿色蓝晶石的宝石学特征

Gemmological Characteristic of Green Kyanite

  • 摘要: 绿色蓝晶石具独特的绿色朦胧观感少见于国内珠宝市场,为了解其宝石学性质与致色机理,运用拉曼光谱、激光剥蚀-电感耦合等离子体质谱(LA-ICP-MS)、紫外-可见吸收光谱(UV-Vis)、光致发光光谱(PL)技术对不同色调绿色蓝晶石进行成分分析与光谱实验。实验表明,绿色蓝晶石朦胧观感来自于宝石内部大量浑圆石英、短针状滑石包裹体,而其绿色则来自Fe、Cr元素电子跃迁产生的选择性吸收。Fe元素与Cr元素分别在蓝紫区和橙红区产生吸收,造成500 nm附近绿色透射窗,随着Fe元素浓度上升,绿色蓝晶石将呈现黄色调,当Cr元素浓度较高时,样品呈蓝绿色调。光致发光光谱显示,波长为410、580 nm光能有效激发样品红色荧光,由于吸收光谱中Fe相关蓝紫区吸收峰存在,造成紫外荧光灯下呈惰性。

     

    Abstract: Green kyanite with unique filmy perception rarely appears in domestic gem market. In order to study its gemmological properties and colour origin, technologies like Raman spectroscopy, laser ablation-inductively coupled plasma mass spectroscopy (LA-ICP-MS), ultraviolet-visible spectroscopy (UV-Vis) and photoluminescence spectroscopy (PL) are resorted together. Spectroscopic results suggest that the filmy perception of the green kyanite comes from massive round quartz and short needle-liked talc inclusions, and its green body colour is ascribed to the selective absorption of the electron transitions of iron (Fe) and chromium (Cr). Fe and Cr absorb light in blue-violet and orange-red region respectively, and result in a green transmission window near 500 nm. With the increase of Fe concentration, samples appear yellowish tone, while a bluish tone appears with the increase of Cr concentration. PL spectra show that 410 nm and 580 nm light can excite the red fluorescence of the samples effectively. Therefore, it is considered that the Fe absorption bands in the ultraviolet region are the cause of the inertia appearance of the green kyanite samples under gemmological ultraviolet fluorescent lamp.

     

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