马达加斯加黄色方柱石的谱学特征研究  

Study on the Spectral Characteristics of Scapolite From Madagascar

作　　者：丁薇 陈全莉[1,2] 艾苏洁 尹作为 DING Wei;CHEN Quan-li;AI Su-jie;YIN Zuo-wei(Gemmological Institute,China University of Geosciences(Wuhan),Wuhan 430074,China;Institute of Jewelry,West Yunnan University of Technology,Tengchong 679118,China)

机构地区：[1]中国地质大学(武汉)珠宝学院,湖北武汉430074 [2]滇西应用技术大学珠宝学院,云南腾冲679118

出　　处：《光谱学与光谱分析》2022年第7期2194-2199,共6页Spectroscopy and Spectral Analysis

基　　金：国家自然科学基金项目(41874105)资助。

摘　　要：利用常规宝石学仪器、电子探针、傅里叶变换红外光谱仪、激光拉曼光谱仪、紫外-可见分光光度计和三维荧光光谱仪等,对马达加斯加黄色方柱石的宝石学性质及谱学特征进行了研究分析。马达加斯加方柱石的宝石学特征与方柱石理论值基本一致;方柱石样品颜色均匀,具有玻璃光泽,原石晶型较为完好且表面普遍可见纵纹及褐红色杂质,部分样品表面可见晕彩效应,样品内部可见多种包裹体,如黑云母、无色晶体包裹体等。红外光谱分析结果表明,样品在指纹区均显示1039,1105和1196 cm^(-1)处Si(Al)—O伸缩振动吸收峰;752 cm^(-1)处Si—Si(Al)伸缩振动吸收峰;551,687和624 cm^(-1)处O—Si(Al)—O弯曲振动吸收峰;459 cm^(-1)处Si—O—Si的弯曲振动与Na(Ca)—O伸缩振动的耦合吸收峰;416 cm^(-1)处Si—O—Si弯曲振动吸收峰。红外光谱官能团区的诊断性鉴定依据为:3530和3592 cm^(-1)处O—H振动引起的吸收峰;2499,2629和2964 cm^(-1)处CO_(3)^(2)振动产生的吸收峰。拉曼光谱分析结果表明,桥氧弯曲振动产生459和538 cm^(-1)两处吸收峰;Al—O振动导致775 cm^(-1)吸收峰;硅氧四面体Q_(4)结构单元振动产生1114 cm^(-1)吸收峰。紫外-可见光吸收光谱可知,马达加斯加方柱石为过渡金属元素致色,铁离子的存在导致了379和420 nm两处吸收峰,且420 nm吸收峰的强弱影响着方柱石的颜色深浅。致色原因为占据了晶体结构中四面体位置的Fe^(2+)与Fe^(3+)之间电荷转移,从而产生黄色。三维荧光光谱分析显示,方柱石具有较为一致的发光行为,均可见一强一弱两个荧光峰,多集中在302 nm(λ_(ex))/343 nm(λ_(em))附近。电子探针成分分析结果表明样品属于方柱石族系列中的针柱石,Ma值范围为66%~69%,平均Ma值为68.1%,且随着Ma值的增高,双折射率随着变小。谱学测试作为无损测试技术,适用于鉴定宝石品种。对鉴定马达加斯加方柱石具有重要的�The gemological and spectroscopic properties of the Madagascar scapolite is studied based on analyses of fifteen samples using EMPA,FTIR,Raman spectroscopy,UV-Vis Spectroscopy,fluorescence spectroscopy and some gemological instruments.The gemological characteristics of Madagascar scapolite are consistent with the theoretical values of scapolite;The samples are uniform in color and have a glassy luster.The raw stone crystal is relatively intact.Longitudinal stripes and maroon impurities are commonly seen on the surface of them.Iridescence can be seen on the surface of some samples,and a variety of inclusions can be seen inside the samples,such as biotite and colorless crystal inclusions.The infrared spectrum analysis shows that absorption peaks of 1039,1105,1196 cm^(-1) in the fingerprint area are attributed to the Si(Al)—O group.752 cm^(-1) peak is due to Si—Si(Al)stretching,551,687,624 cm^(-1) peaks are due to O—Si(Al)—O bending vibration.Bending vibration of Si—O—Si associated with Na(Ca)—O stretching jointly results in a 459 cm^(-1) peak.416 cm^(-1) is due to the bending vibration of Si—O—Si.Absorption peaks related to functional group area are mainly due to different vibrational modes and frequencies of CO_(3)^(2)(2499,2629,2964 cm^(-1))and O—H(3530 and 3592 cm^(-1)),which are diagnostic for the identification of scapolite.The Raman Spectroscopic analysis indicates that the bending vibration of bridge oxygen produces 459 and 538 cm^(-1) peaks;Al—O vibration leads to a 775 cm^(-1) peak.The vibration of SiO_(4) tetrahedron unit generates 1114 cm^(-1).UV-Vis spectrum shows 379 and 420 nm,which are caused by electron transfer between Fe^(2+)and Fe^(3+)in tetrahedron position.The yellow color of Madagascar scapolite is due to transition metal elements.The intensity of the 420 nm peak directly affects the color depth of scapolite.Analysis of 3D luminescence shows a relatively uniform luminescence phenomenon,which shows two fluorescence peaks,one strong and one weak,mostly centered at 302 nm(λ

关 键 词：方柱石 宝石学特征 谱学特征 马达加斯加 

分 类 号：P575.4[天文地球—矿物学]