The conventional gemological properties, chemical composition, crystal structure, and inclusions composition and characteristics of the Nigerian gahnite were analyzed in depth by conventional gemological testing, electron probe, single crystal X-ray diffraction, and Raman spectroscopy. The gahnite exhibits well-preserved octahedral crystal morphology, strong vitreous luster, and semi-transparency, with a relative density ranging from 4.48 to 4.61 and a refractive index of 1.792 to 1.794, displaying inert fluorescence under ultraviolet light. The electron probe analysis determined its chemical formula as Zn_(0.87~0.92)Fe_(0.06~0.07)Al_(1.98~2.01)O₄. Single-crystal X-ray diffraction revealed a cubic crystal system with space group Fd3m, lattice parameter a=8.089(2)Å, tetrahedral bond length T—O=1.953(4)Å, and octahedral bond length M—O=1.912 9(19)Å. Characteristic Raman absorption peaks for gahnite were identified at 418 cm^-1 and 659 cm^-1, corresponding to the E_g mode and high-frequency T_2g(3) mode, respectively. Raman spectroscopy of inclusions confirmed the presence of various minerals in gahnite, including sphalerite, albite, muscovite, quartz, beryl, zircon, and phenacite. Combined with previous studies, it is believed that gahnite in Nigeria is formed in granite-pegmatite rich in Li, Cs, Rb, Be and Ta.