Three-Dimensional Evaluation of Magnetite–Hematite Transformation Via EBSD Technique

Abstract

Previous research has shown that the orientation of the lattice of hematite, originated during the transformation of magnetite to an oxidized phase, is controlled by the original crystal of magnetite. So, to corroborate this study, a three-dimensional characterization was done to verify if this phenomenon can be observed in the same degree along the chief crystallographic planes of magnetite. Thus, well-formed crystals of magnetite partially transformed to hematite were sectioned along the planes {100–111} and analysed via electron backscatter diffraction (EBSD). The results show that in {111} plane, the transformation to hematite is drastic because of the coincidence with the physical surface of the mineral. In this plane, when compared to the {110} and {100}, the new hematite is represented by large crystals. The correlated boundaries between 〈111〉 of magnetite and 〈0001〉 were identified on the three surfaces, whereas the correlation between 〈110〉 of magnetite and 〈11–20〉 of hematite was less remarked. Therefore, it is concluded that the level of phase transformation of magnetite is controlled not only by the crystallography of both minerals involved in the conversion but also by the specific position of the transformed surface in the mineral body.