一种马达加斯加蓝宝石的宝石学及谱学特征  

Gemmological and Spectroscopic Characteristics of Blue Sapphire from Madagascar

作　　者：夏苏琴 姜浩 裴景成[1,2] 赖潇静 XIA Suqin;JIANG Hao;PEI Jingcheng;LAI Xiaojing(Gemmological Institute,China University of Geosciences,Wuhan 430074,China;Hubei Gems and Jewelry Engineering Technology Research Center,Wuhan 430074,China)

机构地区：[1]中国地质大学(武汉)珠宝学院,湖北武汉430074 [2]湖北省珠宝工程技术研究中心,湖北武汉430074

出　　处：《宝石和宝石学杂志（中英文）》2023年第5期73-82,共10页Journal of Gems & Gemmology

基　　金：国家自然科学基金青年科学基金项目(42002041);中国地质大学(武汉)中央高校基本科研业务费专项资金(162301202618)。

摘　　要：马达加斯加蓝宝石目前占据了一定的珠宝市场,然而其宝石学和谱学特征方面的资料仍有待补充。本文以一批马达加斯加蓝宝石样品为研究对象,利用常规宝石学测试仪器、显微拍照、激光剥蚀等离子质谱仪、激光拉曼光谱仪、红外光谱仪、显微紫外-可见-近红外光谱仪研究其宝石学及谱学特征。结果表明,这批马达加斯加蓝宝石样品颜色表现为深浅不一的蓝色调,晶体形态为六方短柱状、桶状、板状,原石表面有三角形生长丘与凹坑;放大观察发现裂理十分发育,内部含有大量愈合裂隙、三角形裂纹、定向排列的赤铁矿与钛铁矿夹杂的针状包裹体、锆石、赤铁矿等固态包裹体以及气液两相包裹体;LA-ICP-MS结果显示其微量元素含量具有高Fe,Ga和低Mg,Cr的特点,且Fe/Ti、Cr/Ga、Fe/Mg、Ga/Mg、Ga/Al比值均偏向玄武岩型成因蓝宝石的地球化学特征;红外光谱表明有微弱3309 cm^(-1)处吸收峰,以及硬水铝石的特征峰2125 cm^(-1)和1990 cm^(-1),指示其未经过热处理;紫外-可见吸收光谱表明,此类马达加斯加蓝宝石样品的颜色与单个Fe^(3+)、Fe^(3+)-Fe^(3+)离子对的d电子跃迁、Fe^(2+)-Ti^(4+)价间电荷转移有关,“肩峰”330 nm与较高的Fe^(3+)浓度密切相关,但Ti元素含量偏低,造成颜色不够鲜艳。Madagascar sapphires currently occupy a significant portion of the jewelry market,however,there is still a need for additional information on their gemmological and spectroscopic characteristics.The gemmological and spectroscopic characteristics of sapphires from Madagascar in this study were investigated by using conventional gemmological test instruments,photomicrograph,laser ablation inductively coupled plasma spectrometer,laser Raman spectrometer,Fourier transform infrared spectrometer,and microscopic UV-Vis-NIR spectrometer.Sapphires from Madagascar in this study are blue with different shades.The crystal morphologies are hexagonal short prism,barrel-shaped form and plate-shaped form,and there are triangular growth mounds and pits on the surface of the rough stone.Magnified observation reveals that the parting is well developed,and there are a large number of healed cleavages,oriented needle-like hematite accompanied with ilmenite inclusions,zircon and hematite solid inclusions,and gas-liquid inclusions inside the sapphire.The results of LA-ICP-MS show that the trace elements are characterized by high Fe and Ga and low Mg and Cr,and the Fe/Ti,Cr/Ga,Fe/Mg,Ga/Mg,and Ga/Al ratios are all biased toward the geochemical characteristics of basaltic sapphires.Infrared spectra show weak 3309 cm^(-1)peak,and strong 2125 cm^(-1)and 1990 cm^(-1)peaks which related to diaspore.These indicate that the sapphire has not been heat-treated.UV-Vis-NIR absorption spectra indicate that the color of sapphires from Madagascar are related to individual Fe^(3+),Fe^(3+)-Fe^(3+)pair d electron leap,and Fe^(2+)-Ti^(4+)intervalence charge transfer.The absorption at 330 nm commonly called“shoulder”,which is closely related to the higher Fe^(3+)element,but the low elemental Ti content causes less vivid color.

关 键 词：蓝宝石 宝石学特征 化学成分 谱学特征 颜色成因 马达加斯加 

分 类 号：TS93[轻工技术与工程]