红外光谱-显微共焦激光拉曼光谱研究天然红宝石和蓝宝石中含水矿物包裹体特征

天然红宝石和蓝宝石的包裹体中常见典型的含水矿物包裹体,这些含水矿物包裹体容易受外界环境升温而发生改变。微量含水矿物包裹体变化会对红宝石和蓝宝石的物理和化学性质产生明显影响,该性质为宝石热处理的鉴定提供了检测思路。本文采集了天然红宝石和蓝宝石样品,用显微镜放大观察包裹体特征,结合红外光谱与显微共焦激光拉曼光谱测试研究了含水矿物包裹体的特征。结果表明:天然红宝石和蓝宝石样品中含水矿物包裹体的外观轮廓清晰,晶形完整;红外光谱在2000～3700cm~(-1)附近显示出2105～2110cm~(-1)和1977～1985cm~(-1)硬水铝石和3619cm~(-1)和3696cm~(-1)高岭石等水(H_2O或—OH等)的特征吸收峰;拉曼光谱中可见角闪石、云母、磷灰石和长石等结晶度较好的典型含水矿物包裹体的特征拉曼位移。该系列特征揭示了红宝石和蓝宝石样品中含有水的特征,可作为红宝石和蓝宝石天然成因且未经过热处理的鉴定依据。

Characterization of Hydrous Mineral Inclusions in Ruby and Sapphire by Infrared Spectroscopy and Microscopic Confocal Laser Raman Spectroscopy

BACKGROUND: There are water molecules and hydrous mineral inclusions in natural ruby and sapphire. The hydrous minerals disappear easily after heat treatment, which causes the physical and chemical properties of ruby and sapphire to change. Thus the hydrous mineral inclusions have important indications for identifying whether or not ruby and sapphire have been heated.
OBJECTIVES: To analyze the characteristics of the hydrous mineral inclusions, and discuss the validity of the identification method for identifying whether or not ruby and sapphire have been heated through hydrous mineral inclusions.
METHODS: Mineral inclusions were characterized by the gem microscope, infrared spectroscopy and microscopic confocal laser Raman spectroscopy.
RESULTS: The hydrous mineral inclusions showed good shape and clear appearance. The infrared spectrum characteristics showed diaspore characteristic absorption peaks at 2105-2110cm^-1 and 1977-1985cm^-1, and kaolinite peaks at 3619cm^-1 and 3696cm^-1. The microscopic confocal laser Raman spectroscopy analysis showed the typical characteristic peaks of hydrous mineral inclusions such as amphibole, mica, apatite and feldspar.
CONCLUSIONS: The features shown in the results reveal the water-containing characteristics of ruby and sapphire samples, which can be used to determine the natural rubies and sapphires without heat treatment.