Formed over 2 billion years ago from multiple injections of magma into the earth’s crust many kilometres below the surface, the Bushveld Complex is geologically unique due to its size, uniformity of its layering and extent of known mineral content. This saucer-shaped intrusion is over 350km wide, 250km long and up to 12km thick. Over time, the rim of the intrusion has been exposed by erosion, revealing three separate main segments known as the Western, Eastern and Northern Limbs. The Western Limb is split into two lobes (north-western and south- western) by the Pilanesberg complex, a remnant of an alkaline volcanic plug intruded into the Bushveld Complex about 1,250 million years ago. The Eastern Limb is split into two lobes (north-eastern and south-eastern) by the north- east trending Steelpoort fault. The exposed segments exhibit layering of pyroxenites, norites, gabbros, anorthosites and chromitites and this layering occurs across the entire extent of the complex. Within the layers, mineralisation is found in specific horizons containing chromium, iron, titanium, vanadium, nickel, copper and PGM.

The Bushveld Complex comprises three main suites, namely the Rooiberg Group, Lebowa Granite Suite and Rustenburg Layered Suite. The Rustenburg Layered Suite comprises four major subdivisions: the Upper Zone, Main Zone, Critical Zone and Lower Zone. Economic concentrations of PGMs occur mainly in three distinct units within the Critical Zone: Merensky Reef; Upper Group 2 (UG2) chromitite; and Platreef. The Merensky Reef and UG2 Reef occur around the Eastern and Western Limbs of the complex, while the Platreef is found only along the eastern edge of the Northern Limb.

The UG2 Reef, which is consistently developed throughout the EL and WL, is rich in chromitite, but with lower gold and base metal content compared to Merensky Reef. In the WL, the UG2 Reef occurs between 12m and 150m vertically below the Merensky Reef and dips at 18º to 27º in a south-easterly direction. In the EL, the reef occurs between 120m and 400m vertically below the Merensky Reef and dips at 8º to 18º in a south-westerly direction.

Kroondal forms part of the South-western Limb of the Bushveld complex and operates under a mining right covering 22km2.

Current infrastructure comprises five decline shafts (Bambanani, K6, Kopaneng, Kwezi and Simunye shafts) and two concentrators.

Kroondal is a partly mechanised bord-and-pillar operation mining UG2 reef exclusively up to a depth of 450m below surface.

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 plants indicate that the ‘watershed’ size where flotation drops off significantly must be relatively fine. This is indicated in, where data collected from a UG2 concentrator illustrate the relative recovery by size fraction in the mainstream roughers and scaven ........