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

Abstract

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.

Keywords

• ruby
• sapphire
• hydrous mineral inclusions
• spectrum characteristics
• heat treatment
• infrared spectroscopy
• microscopic confocal laser raman spectroscopy