MECHANISMS OF TRANSFORMATION OF WEAK MAGNETIC FERRIFEROUS MINERALS (HEMATITE, GOETHITE) IN STRONG MAGNETIC MINERALS (MAGNETITE, MAGHEMITE) UNDER THE INFLUENCE OF EXTERNAL PHYSICAL AND CHEMICAL FACTORS
In order to improve the processing technology of iron ore, the experimental study of regularity and mechanisms of modifying the composition, crystal structure, and magnetic properties of natural ferriferous oxides, oxyhydroxides and hydroxides of iron was conducted. Complex studies of 1) Archean-Paleoproterozoic and Mesoproterozoic ferruginous quartzites, contrastly differing in the degree of metamorphism and chemical weathering; 2) ultrafine oxidic-ferruginous ochres from apoultrabasitic and aposideritic crusts of weathering in the Middle and Southern Ural deposits; 3) ferruginous bauxites from Late Devonian crusts of weathering in the Middle Timan; 4) effects of recovery of iron ions in jaspilites, apojaspilite limonites, ferruginous ochers and ferruginized bauxites with hematite and goethite transformation into magnetite under heating with catalysts in the dry state and in aqueous media were carried out. It was established that ferruginous quartzites, similar in formation but different in age and geological history, significantly vary in mineral composition, microstructure, structural state of minerals, iron crystallochemistry and technological properties. The most important mineralogical and technological properties of iron-oxide formations from weathering crusts are caused by their high dispersion, mainly globular morphology of individuals and a low degree of crystallinity of the constituent ferriferous phases. By the iron crystallochemical distribution, ferruginous bauxites are divided into three varieties, nonidentical by the enrichment and utilization methods. Thermally and electromagnetically stimulated transformations of weakly magnetic iron oxides and oxyhydroxides into magnetite of different stoichiometic degrees were analyzed. The transition was gradual with the formation of intermediate phases. The obtained results opens up the prospect of a very significant improvement of enrichment technology of iron ore and bauxite raw materials.