Variability of Crushability and Grindability of Iron Ores in an Itabirite Deposit

The identification of ore types that share similar geological characteristics and metallurgical performance in a deposit is of great relevance in mine planning. In the case of a low-grade iron ore from Brazil, called itabirite, ore types are usually classified as compact and friable, in addition to canga. As itabirites become more widely exploited, friable itabirites have become scarcer, leaving more competent ores to be processed. The work investigates the response of 19 iron ore samples from the Serra do Sapo deposit (Minas Gerais, Brazil), through a variety of bench-scale comminution tests. In the context of crushing (>25 mm), one subtype of compact itabirite, called supercompact, presented substantially higher resistance to fragmentation than those of compact itabirite and canga. In the context of grinding (<19 mm), an inversion occurs, with canga presenting the highest resistance to comminution, followed by the itabirites (friable, compact, and supercompact), nearly indistinctively. This demonstrates that the relative competence of iron ores to withstand comminution in the studied mineral deposits varies significantly as a function of particle size and, therefore, size reduction stage. Finally, grouping of the samples using cluster analysis demonstrated the relevance of discrimination between compact and supercompact itabirites, besides canga, with supercompact itabirite having a greater affinity to canga than with its compact counterpart. This shows the importance of further discriminating itabirites, particularly in the context of comminution at coarser sizes.