Magnetic susceptibility and temperature measurements have been made in two of three holes drilled in 1975 through the crust and into the still molten lens of tholeiitic basalt in Kilauea Iki lava lake (formed in 1959). The temperature above which magnetic susceptibility drops to zero-the apparent Curie temperature-is 540¿C. at depths of 34.7--35.9 m below the lake surface. These field measurements suggest that the dominant ferromagnetic mineral in the cooling basalt is titanomagnetite containing about 10 mol percent ulv¿spinel.