The Bushveld layered sequence around Modikwa strikes north-northwest to south-southeast and dips to the south-west at 10º to 12º, with local variations in the dip resulting in gradients of nearly 20º. There are several instances where some gentle “rolling” of the reef horizons have been recorded, and normally steeper dips are noted nearer the outcrop (as opposed to at depth).

The outcrop positions of the Merensky Reef and the UG2 Reef normally occur within the areas of low relief, and much of the outcrop is masked by extensive development of black turf as well as, in places, transported sediments. On the farms Maandagshoek 254 KT, Onverwacht 292 KT and Winterveld 293 KT; however, the UG2 Reef (and occasionally the Merensky Reef) outcrops in a series of elongated hills. Although frequently covered with scree material, much of this outcrop has been marked by a series of trenches and pits, many of which date from early pioneer prospecting.

Both the UG2 and Merensky reefs are present at Modikwa. The UG2 Reef occurs as a chromitite layer with an average thickness of approximately 60 centimetres. Three leader chromitites occur above the main seam. Gentle undulations of the UG2 Reef with amplitudes of less than 2 metres are developed across the mine area. Potholes are randomly distributed within the North shaft area but are less abundant in the South shaft area. The Onverwacht Hill area in the southern portion of the mine is characterised by the presence of sev ........

Mining consists of mechanised development and conventional stoping. The UG2 is accessed via two primary declines from the surface, and Merensky 2 shaft.

Capital expenditure at Modikwa Mine related to fleet refurbishment and critical spares, capital development, the Merensky project and installation of a proximity detection system for the mining fleet. Key points on projects include:

• North shaft – level 9 infrastructure works have been completed. The main decline development has reached level 10 and the reef access decline is being established. A downcast shaft to provide additional ventilation for mining levels below 10 will be established around level 9. The process to secure environmental approval for the access road and shaft has advanced, with approval envisaged in 1H F2023;

• South 2 shaft – the shaft has ramped up to steady state production. It achieved an average production run rate of 66 738 tonnes per month, well above the 55 000 tonnes target. Preparation work for the 2.5km underground-to-surface conveyor belt that will enable South 2 shaft to ramp up production to 100 000 tonnes per month is underway;

• Merensky – the bord-and-pillar Merensky shaft was reopened on a trial basis after a prefeasibility study. The shaft was dewatered, and infrastructure established to ramp up production to 30 000 tonnes per month while confirming the project viability before starting the bankable feasibility study.

Run-of-mine tonnage is processed at the Modikwa concentrator and the PGE-rich concentrate is transported to Anglo Platinum’s Polokwane smelter and refining facilities.

The chrome plant was commissioned in August 2021.

PROCESSING PLANT
Froth flotation is the primary mineral processing separation step employed in the beneficiation of PGM ore bodies. Anglo Platinum operates a significant portion of the total installed flotation capacity in the PGM industry, which is installed at 20 operating plants across the Bushveld.

Anglo Platinum has 20 operating concentrators sited around the Eastern, Northern and Western limbs of the Bushveld complex. The concentrators treat mainly Merensky and UG-2 ores, with Potgietersrust (PPL, Sandsloot) and PPRust North being the only two plants designed to treat the Platreef ore.

For typical UG2 ores, for example, the finer natural PGM grain size in the in situ ore and the relative performance of PGM flotation ........