Abstract: The mineral samples from the Shandong jewelry market are used to imitate sapphire and usually called "Youzi" by the native people.The gemmological,mineralogical and spectral characteristics of the mineral samples are studied by using X-ray powder diffraction,Fourier transform infrared spectrometry and electron microprobe.The results show that the imitation sample is single-crystal magnesia spinel.Isomorphous substitution appeared between Mg²⁺ and Fe²⁺,Al³⁺ and Fe³⁺.The magnesia spinel from Changle,Shandong province,is fitted for a common value gemstone because of its strong luster,high hardness and durability.The magnesia spinel has the broad application prospects,significant economic value and huge market potential.