The Platreef mineralisation comprises a variably layered, composite norite–pyroxenite– harzburgite intrusion that lies near the base of the Northern Limb of the Bushveld Complex, in contact with metasedimentary and granitic floor rocks. The variability of lithology and thickness along strike is attributed to underlying structures and assimilation of local country rocks.

Within the Platreef Project area, five major cyclic units have been recognised, which correlate well with the Upper Critical Zone (UCZ) rock sequence described for the main Bushveld Complex. The Turfspruit Cyclic Unit (TCU) is the main mineralised cyclic unit; this unit is analogous to the Merensky Cyclic Unit (MCU) that contains the Merensky anorthosite and pyroxenite and hosts the Bushveld’s principal mineralised reefs. The TCU is laterally continuous across large parts of the Platreef Project area. Mineralisation in the TCU shows generally good continuity and is mostly confined to pegmatoidal orthopyroxenite and harzburgite.

Other cyclic units that have been identified adjacent to the TCU are the Norite Cycles (NC1 and NC2), Pseudo Reef, and the Upper Group 2 (UG2). Contamination of the UCZ units by assimilation of Transvaal Supergroup metasedimentary rocks can occur within any of the stratigraphic horizons; however, in the area being considered for underground mining, contamination is predominantly confined to the units below the TCU.

Within the TCU, high-grade PGE–Ni–Cu mineralisation is consistently hosted within an unconformable, non cumulate, pegmatoidal, mafic to ultramafic sequence, bound by chromitite stringers and containing coarse grained sulphides; this is known as T2, with the mineralised portion referred to as T2MZ. The T2 pegmatoid is subdivided into an upper pyroxenitic unit (T2Upper or T2U) and a lower olivine-bearing pyroxenitic or harzburgitic unit (T2Lower or T2L). Overlying this pegmatoidal package is a non pegmatoidal, feldspathic pyroxenite unit of variable thickness, termed T1.

Mining at Platreef will be performed using a combination of mining methods. Initially, ore zones with vertical thicknesses greater than or equal to 18 m will be mined using the longhole stoping method, while thinner ore zones will be mined using mechanised drift and-fill or driftand-bench methods. All methods require the use of backfill.

A two-phased production approach was used for the Phase 1 flow sheet development and design. The selected flowsheet comprises a common three-stage crushing circuit, feeding crushed material to two milling-flotation modules, each with a capacity of 2 Mtpa. Milling is achieved in a ball mill with classification and rougher flotation in a split high, medium and low-grade circuit. Each concentrate is cleaned in a dedicated cleaner circuit with varying stages and recycles. Flotation is followed by common tailings handling and concentrate thickening filtration and storage.