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 m and 40 m. Both reefs dip at 20° towards the south-east and extend from a depth of 1 100 m to 3 000 m below surface.

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 from a combination of surface exploration boreholes, ongoing prospect drilling from underground development and on-reef mapping in mine excavations.

Merensky Reef
The Merensky Reef is a zone of mineralisation that 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 sub-facies. Sub-types include 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 lesser disruption. This trend is expected to continue throughout the Western extension section.

The Mineral Resource channel is the planned mining cut on the Merensky Reef and 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 mineralised 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 extremely 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. The Mineral Resource channel, comprising these seams, inclusive of a 10 cm portion of mineralised reef footwall, which is the planned mining cut, is in the order of 140 cm to 160 cm thickness. There is no basis for subdividing the UG2 Reef into sub-types.

Historically, UG2 mining has been limited to de-stressed areas underlying previously mined Merensky Reef. A full reef mining cut enhances metal output, hangingwall stability and safe working practices. UG2 operations are migrating to areas where there has been no previous Merensky mining. In these areas, support regimes and layouts similar to those employed on the Merensky Reef are adopted.

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 destressed mining zone. UG2 operations are migrating to areas where there has been no previous Merensky mining. In these areas, support regimes and layouts similar to those employed on the Merensky Reef are adopted.

The underground workings are accessed from a twin vertical shaft system. The Number 1 Shaft extends below 13 level (2 102 m below surface) and Number 2 Shaft serves workings down to 8 level (1 724 m below surface). The shafts have a lateral separation of 90 m and are interconnected at an intermediate pump chamber (IPC) at 1 019 m below surface, as well as on mining 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 ore and waste rock. The relatively narrow vertical separation between the two reef horizons allows for both of these 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 back length of 180 m and allows for six stoping panels of 30 m length each to be established either side of the central 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 ore-pass 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 concentrator plants, 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 hydropower equipment was developed and engineered from the outset of mining at Zondereinde and continues to function successfully.

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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 ........