Abstract: This paper is a study on the gemmological, mineralogical and spectral characteristics of a kind of accessory mineral in sapphire deposit from Changle, Shandong Province by using conventional gemmological methods, reflective microscope, X-ray powder diffractometer, electronic probe X-ray microscopic analyzer and Fourier transform infrared spectrometer.This accessory mineral is black, opaque and magnetic, and is harder than knife in Mohs scales.Under the reflective microscope, the colour of the samples is steel grey and they are opaque, quadrangular and granular.The results of X-ray powder diffraction and electronic probe microanalysis show that the accessory mineral is titanium magnetite.The substitute of isomorphism is very wide in the crystal structure of the samples, but no harmful trace element has been found.Furthermore, the infrared spectrum of samples is basically the same with the standard infrared spectrum of magnetite.