巴基斯坦斯瓦特山谷祖母绿的谱学特征研究  

Spectroscopy Characteristics of Emerald From Swat Valley,Pakistan

作　　者：鲍珮瑾 陈全莉[1,2] 吴燕菡 李璇 赵安迪 BAO Pei-jin;CHEN Quan-li;WU Yan-han;LI Xuan;ZHAO An-di(Gemmological Institute,China University of Geosciences(Wuhan),Wuhan 430074,China;Gemmological Institute,West Yunnan University of Applied Sciences,Dali 671000,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,云南大理671000

出　　处：《光谱学与光谱分析》2023年第1期213-219,共7页Spectroscopy and Spectral Analysis

基　　金：国家自然科学基金项目(41272053);中国地质大学(武汉)珠宝检测技术创新中心基金项目(CIGTXM-201703)资助。

摘　　要：随着哥伦比亚祖母绿矿的日益枯竭,巴基斯坦祖母绿逐渐成为市场的主力军之一,运用常规宝石学仪器、红外光谱仪、激光拉曼光谱仪、紫外-可见-近红外光谱仪(UV-Vis-Nir)和激光剥蚀电感耦合等离子体质谱仪(LA-ICP-MS)对巴基斯坦斯瓦特产区的祖母绿谱学特征进行了较系统的研究。结果表明,巴基斯坦斯瓦特祖母绿颜色整体呈深绿色-深蓝绿色,折射率较高为1.589~1.615。巴基斯坦斯瓦特产区的祖母绿中含有种类和数量较多的内含物,其中三相内含物呈边界清晰平直的矩形且具有明显定向性,与俄罗斯、赞比亚和埃塞俄比亚产区祖母绿的三相内含物接近。根据同一样品不同颜色的紫外-可见-近红外光谱和LA-ICP-MS的分析表明,在颜色较深的区域,紫外-可见-近红外光谱显示相对较强的427,608,637和679 nm(o光)Cr的R线吸收以及在o光下370 nm Fe的吸收,同时此区域内Cr和Fe含量相对较高,因此祖母绿色带是由含量不同的Cr和Fe所致。巴基斯坦斯瓦特祖母绿是由Cr致色,V对颜色有一定贡献且Cr/V极高。根据LA-ICP-MS结合红外光谱可知,巴基斯坦斯瓦特祖母绿属于富碱祖母绿,在红外光谱的指纹区显示了与一般祖母绿相同的振动吸收峰,在中红外区4000~2000 cm^(-1),低强度3518和3700 cm^(-1)为Ⅰ型水不对称伸缩振动,其他的水谱带饱和;中等强度的3232 cm^(-1)为[Fe 2(OH)4]2+多聚合离子吸收谱带;在8000~5000 cm^(-1)近红外光谱区,在垂直于c轴的方向上,5264 cm^(-1)为Ⅰ/Ⅱ型水ν3+ν2合频吸收带,中等7097 cm^(-1)为Ⅱ型水倍频振动峰、弱的7187和6842 cm^(-1)为Ⅰ型水倍频振动峰;在平行c轴方向上,5272 cm^(-1)为Ⅰ/Ⅱ型水ν3+ν2合频吸收带,7073 cm^(-1)为Ⅰ型水的合频振动峰,7185 cm^(-1)为Ⅱ型水的倍频振动峰。总之,巴基斯坦斯瓦特山谷的祖母绿的主要致色离子为Cr^(3+)和Fe^(3+),碱金属离子含量偏高,属于Ⅱ型水为主的祖母绿类型�With the exhaustion of Colombian emerald mins,the emeralds from Swat vally,Pakistan have gradually dominated the market and the systematic research for emeralds from Swat valley,Pakistan is conducted by using conventional gemological instruments,infrared spectrum,Raman spectrum,UV-Vis-Nir spectrum and Laser Ablation(Microprobe)Inductively Coupled Plasma Mass Spectrometry(LA-ICP-MS).The results show that the color of emerald from swat is dark green to dark bluish green,and the refractive index is 1.589~1.615.There are many kinds and quantities of inclusions in the emeralds from Swat,Pakistan.And the three-phase inclusions are rectangular with a clear boundary and obvious orientation,which is close to the three-phase inclusions in the emeralds from Russia,Zambia and Ethiopia.According to the UV-Vis-Nir spectroscopy and LA-ICP-MS analysis of the same sample with different colors,the UV-Vis-Nir spectroscopy show relatively strong R line absorption of 427,608,637 and 679 nm(O light)belonging to Cr in the dark region and absorption of 370 nm belonging to Fe in the o light,and the content of Cr and Fe in this region is relatively high.So emerald bands are caused by different amounts of Cr and Fe.The color of Emerald from Swat,Pakistan,is caused by Cr,and V contributes to color,and Cr/V is very high.According to LA-ICP-MS combined with the infrared spectrum,emerald from Swat,Pakistan belongs to alkali-rich emerald,and the fingerprint region of the infrared spectrum shows the same vibration absorption peak as common emerald.In the middle infrared region of 4000~2000 cm^(-1),low intensity 3518 and 3700 cm^(-1) belong to the asymmetric stretching vibration of typeⅠwater and the other bands caused by water are saturated.The medium strong peak of 3232 cm^(-1) is caused by polymer ion absorption of[Fe 2(OH)4]2+.In the near infrared spectral region of 8000~5000 cm^(-1),the absorption band at 5264 cm^(-1) belongs to the frequency combination absorption ofν3+ν2 of typeⅠ/Ⅱwater in the direction perpendicular to the C-axis,

关 键 词：祖母绿 紫外-可见-近红外光谱 红外光谱 颜色成因 

分 类 号：P5[天文地球—地质学]