Oxidation and Ejection of Nickel and Zinc from Natural and Synthetic Magnetites

Abstract

Abstract An acid dissolution technique was used to determine the distribution of nickel and zinc in large magnetite crystals and in hematite produced by oxidation of these crystals at high temperatures. About 10% Ni and 17% Zn content of crystals were ejected to the surface by this heating. These are smaller proportions than were observed for microcrystalline synthetic magnetites. The surfaces of partly dissolved crystals contained triangular patterns of etchpits and raised Ni‐rich regions, indicating that dissolution did not occur uniformly. Finely ground natural magnetite altered directly to hematite, whereas synthetic magnetite altered to maghemite at low (ca.200°) temperatures. This difference may be associated with the presence of structural water in synthetic magnetites.