The autosem ore characterisation of conglomeratic and banded iron formations

• Clast size distributions are used to suggest liberation grind size for conglomeratic iron ores.
• Micro-band width size distributions are used to suggest minimum liberation grind size for BIF-type iron ores.
• Macro-band width size compositions are used to suggest maximum liberation grind size for BIF-type iron ores.
• Iron ores are ranked according to clast size distributions and micro-band width size distributions.

Image processing is applied in the calculation of clast sizes for conglomeratic type ore and band width mineral distributions/compositions for banded iron formation (BIF) type ores. Hematite band widths are defined according to hematite mass percent thresholds and were developed to act as a bridging concept between microscopic hematite band widths and macroscopic hand specimen band widths. The difficulties of defining clasts against matrices through automated mineralogy include the occurrence of hematite clasts in a hematite matrix making clast boundaries indistinguishable in a QEMSCAN system. Defining clasts according to size is also problematic since hematite can either form matrix when associated with quartz granules or clasts when associated with clay. After mineralogical classification the ores are crushed to determine liberation and grind size characteristics. The correlations between hematite clast size/hematite band width with liberated grind sizes are compared for use in predictive models.