The mine exploits the Platreef, the primary PGM-bearing horizon developed in the Northern Limb of the Bushveld Complex. The reef averages 150m in thickness, with a prominently top- loaded grade profile, hosting optimal Mineralisation in the upper 30m to 40m of the reef package.

The Platreef is developed in the Northern Limb of the Bushveld Complex and can be described as a multiple-pulse mafic magmatic horizon, dominantly pyroxenitic in composition. It averages 150m in thickness, with a prominently top-loaded grade profile, where the optimal Mineralisation is located in the upper 30m to 40m of the package and strikes ~north-south, dipping at an average of 40° to 50° to the west.

In comparison to the Merensky and UG2 reefs, the Platreef is a far thicker and more variable orebody, typified by extensive contact with metasedimentary and granitic floor rocks and assimilation of footwall fragments. The variability of lithology and thickness along strike is attributed to underlying structures and assimilation of local country rocks. This assimilation ranges from shales and banded ironstones in the south, through to dolomites in the centre of the mining area, to granites in the northern portion of the property.

Carbonate floor rocks incorporated into the basal Platreef have been altered to mineralised parapyroxenites and calc-silicates formed during extensive syn-magmatic interaction with high-Mg silicate melts. Towards the north, where the Platreef country rock is Archaean basement granite, partial melting of this protolith has resulted in the formation of a metamorphic rock referred to as a Granofels. The Granofels is present in a prominent interaction zone developed between the base of the Platreef and the underlying basement granite. As a result, the Mineralised horizon defined for the Platreef orebody often incorporates significant portions of the immediate footwall.

At Mogalakwena Mine, the Platreef is structurally affected by dolerite dykes and several predominantly lateral fault systems orientated in a north-east/south-west direction. Zones adjacent to major fault systems constitute areas of no Mineralisation and are discounted as geological losses. The fault systems display normal to reverse fault displacements ranging between 50m and 600m, with up-thrown blocks proving favourable to mine design. The Platreef hosts significant dolomite inclusions in the southern region of the mining area and these also constitute geological loss zones.

Mining of the orebody is by open pit methods whereby material is extracted in vertical benches to create a large open excavation. Benches are mined from top to bottom and are accessed by means of haul roads in the hanging and footwall to connect multiple benches to surface entry and exit points. Open pit mining is the most widely used surface mining method used to extract minerals relatively close to surface by means drilling, blasting, loading-and-hauling. Material is moved by means of truck and shovel to the processing plants, stockpiles, and waste rock dumps along a network of constructed surface road-ways. The walls of an open pit excavation are mined at the maximum allowable slope angle achievable within the specified geotechnical constraints, and berm-offsets are created between benches to reduce the potential risk of rock falls along the overall slope. The final shape
of the excavation is determined by the overall economics of the exploitation process and is generally subdivided into threedimensional phases expanding the open pit to maximise the potential net present value of the mine within specified constraints.

Waste rock from each open pit is placed in close proximity to the open pit activities.

Open pits at Mogalakwena Mine will not be backfilled and all pits will remain as final voids.

There are ore stockpiles within the mining area that consist of low-low-grade material, high-low grade material and oxidised ore. These stockpiles will be processed when there is a requirement for makeup tonnages in the concentrating circuits.

Current mining areas comprise five open pits: Sandsloot, Zwartfontein, Mogalakwena South, North and Central. Pit depths vary from 30m to 260m.

• Ore is transported by haul trucks to the gyratory crusher and by means of conveyors to the mineral processing plant, as well as within the plant;
• Crushing is achieved in three phases using a gyratory crusher as a primary crusher in an open circuit, followed by secondary and tertiary crushing with associated screening;
• Conveyor feeds the primary mills from the crushed ore stockpiles;
• Following exposure of the PGM and base metal surfaces in the milling circuit, reagents are added to the milled product streams to prepare the minerals for flotation.

There are two mineral processing plants at the mine, MNC and MSC.

The PGM’s are extracted from the ore in the form of a concentrate at both MSC and MNC. The concentrate is transported to the AAP Polokwane Smelter for smelting to produce furnace matte. The matte then undergoes an acid converting process at the Waterval Smelter complex in Rustenburg.


FLOTATION.
The separation of the valuable content from the ore takes place in flotation cells where reagents are added to an aerated slurry to produce high-grade PGMbearing concentrate.

SMELTING.
Use of electric furnaces to smelt concentrate to produce a sulfur-rich matte with gangue impurities removed as slag.

SLAG CLEANING.
Converter slag is reduced in an electric furnace to recover PGMs and base metals for recycling back to the converter.

CONVERTING.
Oxygen-enriched air is blown through a topsubmerged lance converter to oxidise sulfur and iron contained in furnace matte to SO2 gas and slag respectively. The resulting converter matte is slow-cooled to concentrate PGMs into a metallic fraction.

MAGNETIC CONCENTRATION PLANT (MCP).
Crushed converter matte is milled and the PGM fraction is separated magnetically. This is pressure leached to yield a solid final concentrate that is sent to PMR. Base metal-rich non-magnetic solids and leach solution are processed further in the base metal refinery.

ACID PLANT.
The SO2 gas is converted to SO3 by passing it over catalytic beds and the subsequent addition of water produces 98% sulfuric acid which is sold to fertiliser manufacturers.

LEACHING.
Base metal-rich solids are leached in high-pressure autoclaves and contacted with MCP leach solution to yield separate nickel and copper streams.

PURIFICATION.
The separate nickel and copper streams are purified. During this process cobalt sulfate is recovered.

ELECTRO-WINNING.
Nickel and copper metal cathodes are produced by passing electrical current through the separate purified stream.

CRYSTALLISATION.
Excess sulfur in solution is neutralised with sodium hydroxide and crystallised to form a sodium sulfate product.

PGM REFINING.
Final concentrate is dissolved using hydrochloric acid and chlorine gas. PGMs are sequentially separated and purified to yield platinum, palladium, iridium, rhodium, ruthenium and gold. Osmium is precipitated as a salt.

Bulk ore sorting pilot plants are already up and running or in the process of being commissioned at Mogalakwena. This technology is helping to significantly reduce our energy and water consumption in line.

The primary benefit of the BOS system is in unlocking production capacity through early rejection of waste or unwanted material, thereby increasing the grade of the ore and reducing the volum that is transported to the processing plant or concentrator. BOS uses composition-sensing technology to detect the concentration of elements of interest, as well as the amount of waste in the material being transported for processing. This has led to a reduction in overall costs per tonne produced, along with a decrease in wet tailings volumes, and in water and energy use.