The formation behavior of spinel-type LiFeSiO4 crystals in the quenching of melts in the Li2O-Fe2O3-SiO2 system was examined. It was found that high quenching rates of 10(3 similar to)10(6)K/min are favorable for the formation of LiFeSiO4 crystals. The rapid quenched samples showed high electrical conductivities of the order of 10(-2)-10(-4)S/cm at room temperature and low activation energy for conduction of 0.1-0.2eV. Both valences of Fe2+ and Fe3+ were present in the melt-quenched samples, and rapid-quenched samples showed ferrimagnetism. It is proposed that the chemical composition of LiFeSiO4 formed in the rapid quenching of melts would be spinel-type Li1+xFe1-x3+Fex2+SiO4. Because the Li1+xFe1-x3+Fex2+SiO4 crystalline phases are metastable, the rapid quenching technique is necessary for their synthesis. The effects of quenching rate and composition on the formation of spinel-type LiFeSiO4 and on the electrical conductivity of quenched samples were discussed.