缅甸帕敢区翡翠及其皮壳的宝石学特征研究

Gemological Characteristics of Jadeite and Its Crust from Hpakant, Burma

摘要: 本文在查阅国内外文献的基础上，采用传统宝石学仪器、红外光谱仪、电子探针对缅甸帕敢区翡翠样品的原生部位和皮壳部位进行了测试与分析。常规宝石学仪器测试数据显示，缅甸帕敢区翡翠原生部分相对密度为3.33，皮壳部分相对密度为3.30，皮壳部分相对密度略小于原生部分。翡翠原生部分的折射率点测为1.665，皮壳部分为1.67。两个样品在紫外荧光等下均显示为惰性。缅甸帕敢区翡翠原生部分及皮壳部分的红外反射光谱均显示为硬玉的特征峰，且受类质同像替代影响整体向低波数方向略微偏移，主要峰值有1064、1049、958、862、668、575、529、475、441 cm⁻¹。通过对翡翠原生部分和皮壳部分样品的电子探针显微分析实验数据总结和比较，可以看出两部分的矿物组成基本相同，主要成分为硬玉(NaAl[Si₂O₆])，除硬玉外还含有少量绿辉石等次要矿物，同时原生部分的化学成分更接近硬玉的标准值。皮壳部分MgO和CaO的质量分数与原生部分相比略微提高，Na₂O和Al₂O₃的质量分数则相对减少，这表明皮壳部分在后期受到了溶蚀作用的影响。

Abstract: On the basis of consulting the literature at home and abroad, this paper uses conventional gemo-logical instruments, infrared spectrometers and electron probes to test and analyze the original and crust parts of jadeite samples in Pago district, Myanmar. The test data of gemological instruments show that the relative density of the original part of Jadeite is 3.33, the relative density of the crust part is 3.30, and the relative density of the crust part is slightly less than that of the original part. The original part of Jadeite is measured to be 1.665 in refractive index point and 1.67 in the crust part. Both samples were shown to be inert under UV fluorescence et al. The infrared reflectance spectra of the original part of jadeite and the crust part of jadeite in Pago district of Myanmar show the characteristic peaks of jadeite, and the whole is slightly shifted to the direction of low wave number due to the homogeneous substitution effect. The main peaks are 1064, 1049, 958, 862, 668, 575, 529, 475, 441 cm⁻¹. Through the summary and comparison of the electron probe microanalysis experimental data of the original part and the crust part of the jade, it can be seen that the mineral composition of the two parts is basically the same, the main component is jadeite (NaAl[Si₂O₆]), besides jadeite also contains a small amount of secondary minerals such as pyroxene, and the chemical composition of the original part is closer to the standard value of jadeite. The mass fractions of MgO and CaO in the crust are slightly higher than those in the original part, while the mass fractions of Na₂O and Al₂O₃ are relatively lower, which indicates that the crust is affected by dissolution in the later stage.