Working with mineral physicists, we find that redox of mineral affects density of lower mantle minerals. We find for similar composition, more oxidized material is less dense than more reduced material. This redox-induced density contrast can cause a rapid ascent and accumulation of oxidized material in the upper mantle, with descent of the denser reduced material to the core-mantle boundary. We suggest that the resulting heterogeneous redox conditions in Earth's interior can contribute to the large low-shear velocity provinces in the lower mantle and the evolution of atmospheric oxygen. Below is a figure of snapshots from geodynamical calculations showing the process of segregation between reduced and oxidized material caused by intrinsic density differences. Red and blue parts represent reduced and oxidized compositions, respectively.