Technological Characterisation of West African Iron Ores in Order to Predict their Performance in the Benefi ciation Process

摘要

This study details a mineralogical and textural characterisation of West African iron ores withrnan emphasis on their behaviour during mineral processing. By means of both qualitative andrnquantitative characterisation, a simulation of the benefi ciation process applied to these iron ores isrnperformed. A series of different analytical tools are used, including:rn? X-Ray Diffraction (XRD) for qualitative mineralogical analysis;rn? qualitative optical microscopy (phase identifi cation, description of micro-textures) and (semi)rnquantitative optical microscopy (counting of particles, phases and textural types); andrn? chemical analysis.rnAll the information provided by these analytical methods are combined into a quantitativernmineralogical and textural analysis, here called 'modal analysis', which enables us to simulate therncapability of West African iron ores to be benefi ciated by magnetic and gravimetric separationrntechniques.rnOn one hand, both qualitative XRD and optical microscopy have revealed the presence of thernfollowing mineralogical phases: magnetite, haematite, goethite and quartz. On the other hand, thernchemical analyses provide us with quantitative inputs expressed as oxides. We have converted thernoxides into mineralogical contents expressed as magnetite, haematite, goethite and quartz. In thisrnway, we build a simple quantitative mineralogical analysis.rnBeside this, the semi-quantitative approach of the characterisation by optical microscopy alsornprovides us with a liberation study, enabling us to split the gangue-bearing content between tworntypes of particles:rn1. liberated gangue-bearing particles, andrn2. composite particles composed by both iron (oxhydr) oxides and gangue-bearing minerals.rnWe have assumed that we could anticipate the behaviour of these two kinds of particles throughrna mineral process, by simulating the removal of at least the liberated particles of gangue. Opticalrnmicroscopy also revealed a trend in the weathering profi le of the Tokadeh ore horizon with arndecrease from bottom to top of magnetite and an increase of both goethite and martite showing arnhigher level of oxidation and hydration in the upper ore horizon.rnWe have applied this removal extent upon the quartz content of the mineralogical quantitativernanalysis and we have re-calculated the quantitative mineralogical analysis considering the expectedrndecrease in the quartz content. Finally, by converting the re-calculated (oxhydr) oxides contents intorniron grades and summing them, we do obtain a fi nal simulated iron grade for the upgraded products.