The two-billion-year-old Bushveld Complex is the largest layered igneous complex in the world, and is the repository for around 85% of known global PGM resources.

The magmatic layering in the RLS is laterally persistent and can be correlated throughout most of the complex. Layering is generally shallow dipping towards the centre of the complex. The RLS stratigraphy is sub-divided into five zones, which are, from lowest to highest, the Marginal Zone, the Lower Zone, the Critical Zone (which is further subdivided into a lower and upper unit), the Main Zone and the Upper Zone.

The Zondereinde mine is situated in the northern portion of the Western Limb of the Bushveld Complex, approximately 30 km south of the town of Thabazimbi in the Limpopo Province. The mining right covers 9 257 hectares, and is underlain by both the Merensky and
UG2 Reefs, which dip at 20° towards the south-east and extend from a depth of 1 100 to 2 900 m below surface.

The Bushveld stratigraphic sequence at Zondereinde is typical of the northern portion of the western limb. The Critical Zone stratigraphy is compressed and dominated by mafic lithologies, with the vertical separation between the Merensky and UG2 Reefs ranging between 20 and 40 m.

While there is lateral continuity of both reefs across the mine property, the Merensky Reef displays a variety of reef sub-types. The distribution of these is determined by a combination of surface exploration boreholes, continuing prospect drilling from underground development and on-reef mapping in mine excavations.

Merensky Reef
The Merensky Reef is a zone of mineralisation which straddles the base of the Merensky cyclic unit. In the area of Zondereinde mine, the Merensky Reef consists of two sub-facies of the Zwartklip facies, namely the Normal and Regional Pothole sub-facies. The latter
may be further subdivided into three sub-types, each of which occurs at a specific stratigraphic level below that of the Normal reef sub-facies. These being NP2 and P2, which constitute the main sources of ore, and FWP2 which, whilst not historically considered a primary mining target due to its undulating morphology in the central portions of the mine, is now successfully exploited in the western portion of the current mining area where it displays less disruption. This trend is expected to continue in the western extension section.

The Mineral Resource cut (mining cut) on the Merensky Reef is dependent upon the reef sub-type mined and the geozone in which it is located. In all mining cuts, the Merensky chromitite is exposed with a minimum of 10 cm of the overlying mineralized Merensky pyroxenite as hangingwall.

UG2 Reef
The UG2 Reef at Zondereinde mine is remarkably conformable when compared with the Merensky Reef. Disruption, in the form of potholes and reef rolls, is limited and localised. The reef consists of three chromitite seams separated by narrow pyroxenite partings. The lower seam, termed the Main member, is generally in the order of 85 cm thick, and is overlain by two Leader seams, each in the order of 15 cm thick.

Total reef thickness, inclusive of a portion of the mineralised reef footwall, is in the order of 150 to 160 cm. There is no geological basis for subdividing the UG2 Reef into facies types.

Mining of the narrow tabular orebodies in the intermediate to deep level mining environment is successfully conducted using a conventional mining method. The mining layout is a breast configuration on both the Merensky and UG2 reefs. The Merensky Reef excavation is backfilled, which has, historically, then been followed by the extraction of UG2 Reef in a de-stressed mining zone.

The underground workings are accessed from a twin vertical shaft system. The Number 1 Shaft extends to 13 Level (2 039 m below surface) and Number 2 Shaft serves workings down to 8 level (1 724 m below surface). The shafts are 90 m apart and are interconnected at an intermediate pump chamber (IPC) at 1 019 m below surface, and also on levels 2, 4, 6, 7, 8 and 9. Workings below 13 Level are serviced by decline access ways, designed to accommodate both people and materials, and equipped with a conveyor belt system that transports the broken rock. The relatively narrow vertical separation between the two ore bodies allows for both to be accessed via the same primary tunnel development.

The vertical interval between levels is 63 m. With the ore body dipping at 20°, this provides a raise length of 180m and allows for six panels of 30 m length each, either side of the raise. Strike gullies are aligned at 10° above the strike direction. A dip gully handles the ore transported via the strike gullies to three ore passes situated in the original raise, all of which are fitted with radial-door control chutes. Ore is transported to the main shaft ore passes via strike drives located below the two reefs, using battery powered, rail bound, locomotives pulling spans of eight hoppers. Broken ore is tipped into a conventional shaft orepass system, with separate rock handling facilities for Merensky Reef, UG2 Reef and waste rock, and then hoisted to surface in skips. At surface, the ore is transported by conveyor belts to the separate Merensky and UG2 concentrators, whilst waste rock is transported to a waste rock pile.

A key success component of mining is the use of hydro-powered equipment such as rock drills and high-pressure water jets in conjunction with electric scraper winches. This equipment was developed and engineered from the outset of mining at Zondereinde and continues to function successfully.

Surface infrastructure comprises two concentrator plants for Merensky and UG2 ore, a recently expanded smelter which houses two furnaces and a base metals removal plant.[2019 AR, 62]

Concentrating: Merensky and UG2 plants
• In the crushing/screening circuit the ore is crushed to reduce its size before it reports into the mill.
• Merensky ore feeds into a fully autogenous (FAG) mill. In the UG2 plant, the ore feeds into a high pressure grinding roll crusher and then into a primary ball mill.

Surface infrastructure comprises two concentrator plants for Merensky and UG2 ore, a recently expanded smelter which houses two furnaces and a base metals removal plant.[2019 AR, 62]

Concentrating: Merensky and UG2 plants
• In the crushing/screening circuit the ore is crushed to reduce its size before it reports into the mill.
• Merensky ore feeds into a fully autogenous (FAG) mill. In the UG2 plant, the ore feeds into a high pressure grinding roll crusher and then into a primary ball mill.
• The flotation circuit includes rougher cells, scavenger cells and cleaner columns. External sparger column cells act as a cleaner and this helps to produce a final UG2 concentrate with significantly lower chrome content while maintaining PGM recoveries.

Base metal recovery
By-product metals, copper and nickel sulphate, are extracted at the on-site base metals removal plant and sold in the domestic market.

Smelting
The existing smelter at th ........