Both the Merensky and UG2 Reefs, which are contained in the Rustenburg Layered Suite, a welllayered ultramafic to mafic igneous succession on the two billion year-old Bushveld Complex, are present throughout the lease area.

The Merensky and UG2 Reefs are separated by a sequence of primarily anorthositic and noritic layered units from 45m in the northern part of the lease area and thickening to 125m in the southern lease area. Both the Merensky and UG2 Reefs are exploited at Impala Rustenburg.

The Merensky Reef is generally composed of an upper feldspathic pyroxenite, overlying a thin basal chromitite stringer, followed by an anorthosite to norite footwall. Locally this is termed a ‘pyroxenite reef’. Occasionally a pegmatoidal pyroxenite and a second chromitite stringer may be developed between the feldspathic pyroxenite and the footwall units. Locally this pegmatoidal pyroxenite can exceed 2m in thickness. This is termed a ‘pegmatoid reef’.

The UG2 Reef is defined as the main chromitite layer, with most PGM and base metal mineralisation confined to this unit, with a poorly mineralised pegmatoidal pyroxenite footwall. The main chromitite layer’s hangingwall is a feldspathic pyroxenite containing up to four thin, poorly mineralised chromitite layers. The vertical grade distribution is depicted in the accompanying graphs, showing peak values at reef contacts associated with chromitite. The average 6E metal ratios show the distinct differences bet ........

The Merensky and UG2 Reefs are mined concurrently. Stoping at the operations is carried out through conventional double-sided breast mining following Impala's best practice principles. The access haulages are developed in opposite directions from cross-cuts connected to a central shaft position, following the two reef horizons on strike in the footwall of the reefs and are defined as half levels. Footwall drives are developed at approximately 18m to 30m below the reef horizon, with on-reef raise/winze connections between 180m and 250m apart. Panel face lengths vary from 15m to 28m for both Merensky and UG2 Reefs, with panels typically separated by 6m x 3m grid pillars with 2m ventilation holes. Stoping widths are approximately 1.3m and 1.1m for conventional Merensky and UG2 Reefs, respectively, depending on the width of the economic reef horizon. In addition, mechanised (trackless) bord and pillar mining occurs in selected Merensky Reef areas at 14 Decline. The average stoping width of the mechanised panels is about 1.9m.

• conventional mining: Utilises underground conventional stoping to conduct mining operations. The underground tunnel development is drilled using handheld compressed air powered rockdrills, the subsequent hole drilled for rock extraction are filled with explosives and blasted at a set time. The blasted rocks are extracted, pulled to the main rock transfer system and then hoisted to surface. In underground conventional stoping the cleaning of the ........

Processing receives ore from the shafts which is allocated to either the UG2 Plant, for the higher chromium grade material, or the Central Concentrator for Merensky ore. Between 89% and 91% of the PGMs from the Merensky ore are recovered at mass pulls ranging from 5% to 7% utilising 10 primary mills, feeding two, nine stage, tank cell flotation banks. Tailings from this section are milled for further liberation and floated in conventional cells to achieve the aforementioned recovery.

Approximately 79% to 81% of the PGMs are recovered from the UG2 ore at a mass pull of 2% to 3%. The PGM recovery from UG2 ore is performed utilising a more complex circuit configuration to reduce chromium reporting to the concentrate stream. The MF2 Plant, also situated at the Central Concentrator, operates three primary mills that can accommodate any Merensky ore spillover and, more recently, the old tailings from TSF1 and TSF2. This allows for flexibility in the ore split received from the min ........