Role of the silicate phase of an enclosing rock in the prereduction of disseminated chromium ores

Abstract

The composition and distribution of the products of solid-phase metal reduction from disseminated chromium ores are studied. Reduction is shown to occur in these ores despite the presence of isolating layers, which are made from the silicate phase of the enclosing ore, between a reducer and an ore grain. The channels of rapid reduction propagation inside ore grains are cracks filled with silicates. The propagation of reduction through the silicate phases is caused by favorable (as compared to chromospinellides) conditions for the motion of charged oxygen vacancies and oxygen, since these phases are in a glass state at the reduction temperature. The absence of boundaries and lattice defects in the glass state decreases the concentration of dislocation barriers. The low concentration of reducible cations in the silicates causes their motion to vacancy sinks, where reduced metals are accumulated. © 2007 Pleiades Publishing, Ltd.