Fabric and structural characteristics of the martitization process

Abstract

The replacement of magnetite by hematite is not by octant sectors but is independent of sample coordinates and is penetrative to at least the scale of developed [111] parting. Anisotropy increases with depth into the octahedron. Hematite c-axis orientation perfection occurs 5 mm deep into the crystal. The replacement process consists of initial iron atom diffusion through an oxygen framework leading to maghemite, followed by inversion of maghemite to hematite and the development of a distorted octahedron. Deposition of oxidized iron from the diffusion process combined with contraction caused the reduction in the angle (111)--(111) from 70.5 degrees to 67 degrees and the concave and convex (111) faces in the distorted martite octahedra.