无色透锂长石的宝石学特征  

Gemmological Characteristic of Colorless Petalite

作　　者：余炼钢 廖任庆 YU Liangang;LIAO Renqing(Dehong Teachers'College, Dehong, Yunan 678400 China;Shenzhen Institute of Technology,Shenzhen 518100 China)

机构地区：[1]德宏师范高等专科学校,云南德宏678400 [2]深圳技术学院,广东深圳518100

出　　处：《超硬材料工程》2021年第5期51-58,共8页Superhard Material Engineering

摘　　要：利用常规仪器及大型珠宝检测仪器对两粒无色样品的宝石学及谱学特征进行分析研究,结果显示,样品密度约为2.33±0.01g/cm^(3),折射率在1.505~1.523之间,双折射率在0.015~0.017之间,放大观察可见明显的后刻面棱重影线,以及少量短柱状晶体包体,短波紫外光下呈中等紫红色荧光。化学成分分析表明样品Al、Si、O含量高,K、Ca、C1含量低;红外吸收光谱显示1137、1082、1033 cm^(-1)处吸收峰归为[SiO_(4)]^(4-)四面体中Si-O伸缩振动,754、731、704 cm^(-1)处吸收峰归为[AlO_(4)]^(5-)四面体Al-O-Al及[SiO_(4)]^(4-)四面体Si-O-Si的弯曲振动,543、524、494、417 cm^(-1)处吸收峰为Si-O-Si及Li-O-Li的弯曲振动所致;拉曼光谱显示283、318、358、382、467、490 cm^(-1)处特征拉曼位移峰,与[SiO_(4)]^(4-)及[AlO_(4)]^(5-)配位体振动模式相关;紫外-可见光谱显示在可见光区基本无吸收。综合结果表明样品为市场上少见的透锂长石,以高双折射率、较低密度及显微镜下的“重影线”特征与其他长石品种相区分。The gemological and spectroscopic characteristics of the two colorless samples are analyzed and studied with conventional gemological instruments and large jewelry testing instruments during daily teaching activity.The result shows that the density of the samples is 2.33±0.01,the refractive index is between 1.505 and 1.523,and the birefringence-index is between 0.015 and 0.017.The magnified observation shows obvious rear faceted edge double lines,as well as a small amount of short columnar crystal inclusions,and there shows medium purple-red fluorescence under short-wave ultraviolet light.Chemical composition analysis shows that the samples have high contents of Al,Si,O and low contents of K,Ca,Cl.Infrared absorption spectra shows that the absorption peaks at 1137,1082 and 1033 cm^(-1) are attributed to Si-O stretching vibration in[SiO_(4)]^(4-)tetrahedron,and the absorption peaks at 754,731 and 704 cm^(-1) are attributed to bending vibration of[AlO_(4)]^(5-)tetrahedron Al-O-Al and[SiO_(4)]^(4-)tetrahedron Si-O-Si.The absorption peaks at 543,524,494 and 417 cm^(-1) are caused by Si-O-Si and Li-O-Li bending vibration.Raman spectra shows characteristic Raman displacement peaks at 283,318,358,382,467,490 cm^(-1),which are correlated with[SiO_(4)]^(4-)and[AlO_(4)]^(5-)ligand vibration modes.The Uv-vis spectrum of the samples indicate that there is no absorption in the visible region.The comprehensive result shows that the sample is a rare gemstone called petalite in the jewellery market.It is distinguished from other feldspar varieties by high birefringence index,low density and double line of rear facet edge under microscope.

关 键 词：透锂长石 双折射率 宝石学特征 谱学特征 

分 类 号：TS933[轻工技术与工程]