The transformations of magnetite and hematite, which are main existing forms of iron oxides in nature, have been debated for many years. The transformation of magnetite and hematite in nature has generally been considered as a result of a redox reaction and linked to a specific oxidant or reductant. However, a nonredox reaction mechanism was proposed in recent years and it might be helpful in better understanding the complicated mineralization process. Ore textures caused by replacement of hematite and magnetite in natural environment was summarized in this paper. The nonredox reactions might exist in many different mineralization processes on the basis of evidences from studying on BIF and experimental ways. Mechanisms for the transformations of magnetite and hematite provide important significances both in theoretical and practical aspects: one hand, it indicates that the presence of magnetite and hematite in geologic formations may not provide meaningful information on the redox state of fluid; the other hand, it will provide new exploration strategies for hematite rich secondary ores, extending the target for orebodies to deep zones below the paleosurface.