The growth of hematite by oxidation of iron-bearing olivine

The controlled oxidation of iron-bearing olivine has been performed by the repeated annealing and re-examination of thin TEM specimens. With an annealing temperature of ≈900°C, particles of hematite are formed on the surface, leaving an iron-depleted olivine. Thin olivine TEM specimens with a [010] foil normal produce hematite islands with an orientation relationship determined by (100)0{norm of matrix}(0001)h:[001]0{norm of matrix}[1010]h or (100)0{norm of matrix}(0001)h:[001]0{norm of matrix}[1010]h. The hematite particles show strong faceting parallel to the {0001}, {1010} and {1012: planes and, with prolonged annealing, may grow together to produce twin boundaries which are parallel to {0001} or {1010} planes. Neglecting the small lattice mismatch, the "close-packed" planes are continuous across all of these interfaces. © 1989.