Gemmological Characteristic of Spinel Associated Colourless Sapphire

Abstract

The gemmological characteristics of a kind of sapphire that is associated with purple spinel were studied by EDXRF, Raman spectrometer, and fluorescence spectrometer. The sapphire sample contains 99.56% of Al2O3 and a certain amount of SiO2, CaO, TiO2, Fe2O3, Ga2O3, etc.Raman spectra showed that the colourless region is sapphire and the purple region is spinel; the inclusions are irregular and regular hexagonal solid graphite inclusion, gas inclusion that contains CO2, liquid inclusion that contains CH4, healing crack, etc. Fluorescence spectra showed no fluorescence in the colourless and purple substrate, and the peak positions of the fluorescence center of the luminescent part were near 440 nm and 460 nm. With the change of excitation wavelength from 365 nm to 390 nm, the red shift of the fluorescence center occurs. The relative intensity of the fluorescence center at 440 nm and 460 nm changed from strong to weak.