Electrical properties in the Earth's interior are obtained through geoelectromagnetic observations, and are used to infer constituent materials and temperature. Because electrical properties are very sensitive to the existence of liquids, they are used to detect water and melt in the crust and the mantle. Interpreting observed data requires a good understanding of the electrical properties of crust and mantle materials. In this paper, I review the state of our understanding of rock electrical properties. First, I relate macroscopic electrical conductivity and permittivity to microscopic material parameters. Our understanding of the electrical properties of rock-forming minerals and liquids is reviewed from the viewpoint of microscopic structures, and then the properties of rocks are discussed through the effective medium theory. Finally, I point out problems that should be tackled to get a better understanding of the electrical properties of rocks. They are (1) the physics of the electrical conduction in crustal rocks, (2) the distribution of conductive minerals in rocks, (3) the fluid distribution in rocks, (4) the properties of thin fluid film, and (5) the nature of interfacial polarization of fluid-bearing rocks.
