Geometallurgical characterisation of a Channel Iron Deposit (CID) Ore

Channel iron deposits (CID), comprising pisolitic or goethitic ores, remain a prominent iron ore resource in Western Australia. Previous research work on CID pointed out their complexity in genesis, geology, geomorphology, and petrology, which provides some basic information for downstream processing. Sintering investigations have mainly focused on the overall sintering performance and the quality of sinter products rather than the behaviour of the ore components during sintering. However, individual mineral phases in the ores have their own characteristics during reaction with fluxing materials in the sintering process. In this study, the complex mineral phases in a CID goethitic ore are compared with traditional hematite ore. They are classified into several categories based on the mineral composition, including the basic mineral phases: goethite matrix, hydro-hematite, and quartz, and combined minerals: quartz-dispersed hydro-hematite, quartz-dispersed goethite, goethite with dispersed quartz and clay (gibbsite/kaolinite), and ferruginised wood. The changes of the goethitic ore when heated to different temperatures were also investigated. More cracks appeared in the ore with increasing temperature due to dehydration of the goethite matrix. The temperature induced goethite-to-hematite transformation occurred between 260°C and 300°C, as shown in TGA-DSC curves and confirmed by XRD analysis. The colour of the goethitic ore changed from brown to vermillion after 300°C due to the phase transformation, and to ochreous at 1150°C and further to black above 1250°C due to the decomposition of hematite to magnetite.