The dc conductivity of natural single-crystal α-Fe2O3 was measured as a function of O partial pressure from 10−4 to 1 atm at 950° to 1422°C. The conductivity was independent of O2 partial pressure, indicating that hematite is an intrinsic semiconductor with lattice defect concentrations much lower than the concentration of intrinsic electrons (holes). The activation energy of the dc conductivity was 1.18 eV. The iron tracer (55Fe) diffusion coefficients, measured as a function of O2 partial pressure at 1200° and 1300°C, increased as the O2 partial pressure decreased, with a pressure dependence of -0.75; the iron therefore migrates interstitially.