The Prominent Hill iron oxide copper gold (IOCG) deposit is located in the northeastern portion of the Archaean to Mesoproterozoic Gawler Craton, South Australia. Copper-gold-silver mineralisation at Prominent Hill is mostly hosted within hematitematrix breccia containing fragments of sandstone, siltstone, dolostone, and mafic to intermediate volcanic rocks. Copper mineralisation occurs as disseminations of chalcocite, bornite and chalcopyrite in the matrix of the breccia. The Prominent Hill Open Pit Mineral Resource was fully depleted, with the Open Pit mining operations completed in March 2018. Since 2 quarter 2018, previously stockpiled ore is processed. The ROM stockpiles have been classified as Measured because they have been mined from zones which have been drilled to grade-control spacing. Mining production and reclaim records in conjunction with ROM surveys have supported the construction of open pit ROM stockpile block models at a monthly level of definition.

Prominent Hill is a copper, gold and silver mine located 650 km northwest of Adelaide in South Australia and comprise: -Open pit mine (Malu) - which concluded operations in Q1 2018; -Stockpiles - being in operation since Q2 2018; Surface operations to rehandle stockpiles are carried out by mining contractor. Ore in stockpiles is enough to operate until 2025

Crushing and Grinding
Ore is hauled from the mine directly to the primary crusher or stockpiled on the ROM pad until such time as it can be processed. Mineralised waste is stockpiled separately to allow for future reprocessing should this be determined to be economically viable.

The ore is taken from the mine or reclaimed from the ROM stockpiles and tipped into the primary crusher, located adjacent to the ROM pad, where it is crushed to a size of less than 125 mm. The nominal crusher throughput is up to 3,600 tonnes per hour, approximately three times the throughput of the grinding circuit. The ore is then conveyed to the crushed ore stockpile. It is reclaimed from the bottom of the stockpile and conveyed to the semi-autogenous grinding (SAG) mill which operates in a closed circuit with a vibrating screen and pebble recycle circuit. Grinding balls at 125 mm are added including water inside the SAG mill to reduce the ore to micron size contained in a slurry form. Material that doesn’t pass through the 5 x 20 mm screen is recycled back to the SAG mill for further grinding. The slurry containing the fine material that passes through the 5 x 20 mm screen is combined along with the ball mill discharge to slurry feed the primary hydrocylone pack for classification. The primary hydrocyclone separates the material by size, where the overflow fines report to flotation, and the underflow coarse returns to the ball mill where 60 mm balls are added for further grinding. The SAG and ball mill operates in closed circuit with the primary hydrocyclone pack. Dust generation occurs during the dry stages of crushing and when transporting ore to the coarse ore stockpile (COS). Water sprays are used in the crusher pocket and at the discharge of the first conveyor (CV1) to manage the dust. The rest of the size reduction process (grinding) is a wet process where no dust is generated.

The SAG/ball milling circuit enables 80% of the material is sized to less than 125 µm, and becomes suitable for further processing.

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