The Moon is thought to have formed from a giant impact with the Earth. Following its re-accretion, the subsequent cooling and bottom-up fractional crystallization of the lunar magma ocean led to the structuration and layering of the Moon’s mantle. However, lunar seismic data highlight an anomalous low-velocity zone along the core-mantle boundary. Based on recent tidal deformation models, this anomaly is best explained by the accumulation of a high-density and low-viscosity component along the core-mantle boundary. Ilmenite (FeTiO3) is a mineral that precipitates during the late stages of the fractional crystallization of the lunar magma ocean, making it one of the last minerals to crystallize at the top of the rock column. Its high density (≈ 4500 kg.m-3) causes gravitational instabilities that eventually led to the overturn of the lunar mantle, so that ilmenite accumulated at the bottom of the rock column. In this work, we investigated the accumulation of ilmenite (FeTiO3) as the source for the observed anomalous layer at the bottom of the Moon’s mantle. To do so, we experimentally determined the velocity-density relations of lunar mantle compositions with varying amounts of ilmenite in the pressure-temperature conditions representative of the lunar mantle. Several mineral phases co-exist in such complex samples, making conventional X-ray diffraction methods poorly suited to determine the bulk density. As such, we were pushed to lead a novel development on the UToPEC press of the PSICHÉ beamline (synchrotron SOLEIL, Paris) to determine the bulk physical properties of complex multi-phase samples by combining quasi-simultaneously a range of synchrotron techniques (ultrasonic interferometry, white beam Beer-Lambert absorption and pink beam tomography). This development was successfully benchmarked against a reference mineral: olivine. We then conducted a series of experiments that show that while ilmenite is able to cause the observed increase in density, it is however unable to reproduce the magnitude of elastic wave velocity reduction that is detected from seismic data.