Researchers at Ehime University have reported the sound velocity of MgSiO3 Majorite garnet up to the pressure of 18 gigapascals and temperature up to 2,000 Kelvins. Their results lead to understanding of the mineral composition of the Earth's mantle transition zone (MTZ), which has not been fully elucidated yet. This study suggests that a mechanical mixture of slab and mantle rocks, rather than equilibrated rocks, is more likely to explain seismological observations throughout the MTZ.