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 mineralisation consists of lenses found across four main zones:
• Malu, the main mineralised corridor that plunges down from the base of the open pit;
• Ankata, an area to the west of Malu and relatively close to surface;
• Kalaya, an area directly to the west of Malu; and
• Papa, a small area of mineralisation to the east of the open pit.

Prominent Hill is a well established underground copper, gold and silver mine located 650 km northwest of Adelaide in South Australia.

In 2018, the mine converted from open pit to underground-only operations and ramped up to 4 Mtpa in 2020.

The Prominent Hill mineralisation consists of lenses found across four main zones:
• Malu, the main mineralised corridor that plunges down from the base of the open pit;
• Ankata, an area to the west of Malu and relatively close to surface;
• Kalaya, an area directly to the west of Malu; and
• Papa, a small area of mineralisation to the east of the open pit.

Access to the ore body and ore haulage is carried out via decline (ramp) system.

The Prominent Hill Underground Mineral Resource is being mined successfully using sub-level open stoping (SLOS) with cemented fill. Operations are performed by mining contractor.

Prominent Hill is an operating mine and has the majority of necessary infrastructure in place for its continued operation.

Two new primary ventilation fans were commissioned in Q2 2020. This is the third pair of primary ventilation fans installed at Prominent Hill.

A second paste fill plant was successfully commissioned in mid-2020 and is capable of providing cemented fill at a rate to support forecasted production rates.

Prominent Hill Expansion Study update was released on November 16, 2020 and confirms the installation of a 1,360 metre, 7.5 metre diameter vertical shaft at Prominent Hill is technically and economically feasible with capital investment consistent across the interim and strengthened cases. The robustness of the investment into the shaft was tested by examining the feasibility of mining the existing Ore Reserves with a production target based on approximately 6 Mtpa from 2025 comprising less than 30% Inferred Mineral Resource.

The Prominent Hill processing plant has been operating since February 2009 and comprises a conventional crushing, grinding and flotation circuit to recover copper, gold and silver to produce a high-quality concentrate. The plant can process approximately ten million tonnes per annum subject to the ore blend.

The current life of mine schedule has the plant running at that capacity approximately eight to nine million tonnes per annum until the end of quarter one 2025 with a high proportion of stockpiled open pit gold and lower grade ore. On exhaustion of these gold and marginal ore stocks the plant will be fed with underground ore alone.