一例铁斧石的颜色成因及光谱学表征  

Color genesis and spectral characterization of the feraxinite sample

作　　者：余炼钢 廖任庆[2] YU Liangang;LIAO Renqing(Dehong Teachers’College,Dehong 678400,China;Shenzhen Technician College,Shenzhen 518100,China)

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

出　　处：《超硬材料工程》2023年第1期56-60,共5页Superhard Material Engineering

基　　金：2023年云南省教育厅科学研究基金项目(2023J1710)。

摘　　要：斧石是自然界较为罕见的宝石品种,以颜色艳丽及强三色性著称。运用常规宝石仪器及多种测试技术对一例褐黄色斧石的宝石学特征、化学成分及谱学特征进行研究。结果显示:斧石样品的密度为3.186 g/cm^(3),折射率为1.665~1.676。X-射线荧光光谱分析表明其由Al、Si、Ca、Fe、Mn、O等元素组成,铁质系数F=FeO/(FeO+MnO)=0.964,Fe含量远高于Mn,据晶体化学结构特征将其归为含锰质铁斧石。综合化学成分及紫外可见光谱特征表明,其颜色由Fe^(2+)和Mn^(2+)共同作用所致,418、488 nm处的吸收峰由Mn^(2+)离子d-d电子跃迁引起,分别归属于Mn^(2+)的6A^(1g)→4T^(2g)(G)能级跃迁及6A^(1g)→4T^(1g)(G)能级跃迁;451、512、581 nm处的吸收峰由Fe^(2+)离子d-d电子跃迁引起,分别归属于Fe^(2+)离子中5 E g→3E 1g(3 H)能级跃迁及5 E g→3T^(1g)(3 H)能级跃迁。红外反射光谱测试指示环状硅氧骨干结构及多种配位体基团的振动特征,1090、1028 cm^(-1)处的吸收峰分别归属于υ_(as)(Si—O—Si)反对称伸缩振动、υ_(as)(O—Si—O)反对称伸缩振动及υ_(s)(BO_(3))对称伸缩振动联合所致,983 cm^(-1)处的吸收峰归于υ_(s)(O—Si—O)对称伸缩振动,790 cm^(-1)处的吸收峰归属于δ(BO_(3))弯曲振动。拉曼光谱测试显示一组特征拉曼峰,与[SiO_(4)]四面体、[AlO_(6)]八面体及[BO_(3)]三角形等配位体的振动模式相对应,320、395 cm^(-1)处的拉曼峰为Al—O的弯曲振动所致,1007、983 cm^(-1)处的拉曼峰为Si—O对称伸缩振动所致,716、770 cm^(-1)处的拉曼峰为B—O的伸缩振动所致。红外光谱法及拉曼光谱法基于配位体基团振动模式的解析和表征,可作为区分斧石及颜色相似宝石的诊断性依据。Axinite is a rare gemstone in nature.It is known for the pretty color and strong trichromatic feature.Conventional gemological instruments and various testing techniques are used to study the gemological characteristics,chemical composition and spectral feature of a brown axinite sample.The experimental result shows that the density is 3.186 g/cm^(3),and the refractive index is 1.665-1.676.X-ray fluorescence spectrum analysis indicates that the sample is composed of Al,Si,Ca,Fe,Mn and O element,and the iron coefficient value F=FeO/(FeO+MnO)=0.964.The content of Fe element is much higher than that of Mn.According to the crystallochemical structure characteristics,it should be classified as manganese-containing iron axinite.The chemical composition and ultraviolet-visible spectral characteristics shows that its color is caused by the interaction of Fe^(2+)and Mn^(2+).The absorption peaks at 418 nm and 488nm are caused by the d-d electron transition of Mn^(2+)ion,which are attributed to the 6A^(1g)→4T^(2g)(G)and 6A^(1g)→4T^(1g)(G)energy level transitions of Mn^(2+),respectively.The absorption peaks at 451 nm,512 nm and 581 nm are caused by d-d electron transitions of Fe^(2+)ions,which are attributed to the 5 E g→3E 1g(3 H)and 5 E g→3T^(1g)(3 H)level transitions of Fe^(2+)ions,respectively.Infrared reflection-spectrum testing result indicates the vibration characteristics of annular silico-oxygen backbone structure and various ligand groups.The absorption peaks at 1090 cm^(-1)and 1028 cm^(-1)are attributed toυ_(as)(Si—O—Si)antisymmetric stretching vibration,υ_(as)(O—Si—O)antisymmetric telescopic vibration andυ_(s)(BO_(3))symmetric stretching vibration,respectively.The absorption peak at 983 cm^(-1)is attributed toυ_(s)(O—Si—O)symmetric stretching vibration.The absorption peak at 790 cm^(-1)is attributed to theδ(BO_(3))bending vibration.Raman spectroscopy result has revealed a set of characteristic Raman peaks corresponding to the vibration patterns of the tetrahedron[SiO_(4)],the octahedron[A

关 键 词：铁斧石 化学成分 颜色成因 光谱特征 

分 类 号：TS933[轻工技术与工程]