Gemmological Characteristic of Spinel Associated Colourless Sapphire

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.