The Merensky Reef is generally regarded as a uniform reef type, large variations occur in reef thickness, reef composition, as well as the position of the mineralisation.

The rock-forming minerals of the Merensky Reef comprise approximately equal amounts of dark iron-magnesium silicate minerals and lighter calcium-aluminium-sodium silicate minerals (called a feldspathic pyroxenite) under- and overlain by thin (5 to 15 mm) often discontinuous layers of chrornite concentrations. The total thickness of this package is generally less than 30 cm. This zone, commonly known as the Merensky pegmatoid, contains the base metal sulfide grains and associated platinum group minerals. The Merensky Reef has been traced for 300 km around the entire outcrop of the eastern and western limbs of the Bushveld Complex, and to depths of 5 km.

The rock-forming silicate minerals of the Merensky Reef consist predominantly of orthopyroxene (- 60 per cent), plagioclase feldspar (- 20 per cent), pyroxene (- 15 per cent), phlogopite (5 per cent), and occasional olivine which lists the composition of some of the common minerals found in the Bushveld-type rocks. Secondary minerals such as talc, serpentine, chlorite and magnetite have widespread occurrence.

The base metal sulfides consist of pyrrhotite (-40 per cent), pentlandite (- 30 per cent), chalcopyrite (- 15 per cent), and trace amounts of millerite (NiS), troilite (FeS), pyrite (FeSJ, and cubanite (Cu5FeS4). The major platinum group minerals are cooperite (PtS), braggite [(Pt,Pd)NiS], sperrylite (DtAsz) and PGE alloys, although in some areas minerals such as laurite) can be abundant.

The UG-2 Reef is a platiniferous chromititc layer which, depending on the geographic ocation within the Complex, is developed some 20 to 400 metres below the better known Merensky Reef. The chromitite itself is usually 1 m thick but can vary from - 0.4 to up to 2.5 m. Thin chromitite seams (generally less than 20 cm in thickness) may be present in both the footwall and, more commonly, in the hanging wall rocks. The UG-2 consists predominantly of chromite (60 to 90 per cent by volume) with lesser silicate minerals (5 to 30 per cent pyroxene, and 1 to 10 per cent plagioclase). Other minerals, present in minor concentrations, can include the silicates: phlogopite and biotite, the oxides: ilmenite, rutile and magnetite, and base metal sulfides. Secondary minerals include quartz, serpentine and talc.

The base metal distribution follows a similar trend to that of the PGE, with mat of the values occurring in the bottom and top part of the reef. The base metal content of a typical UG-2 Reef is approximately 200 to 300 ppm nickel occurring as nickel sulfide and less than 200 ppm copper occurring as copper iron sulfide.

The platinum group minerals present in the UG-2 Reef are highly variable, but generally the UG 2 is characterised by the presence of abundant PGE sulfides, comprising predominantly laurite (RuOsIr sulfide), cooperite (PtS), braggite (Pt, Pd, NiS), and an unnamed PtRhCuS. The platinum group minerals only reach an average size of approximately 12 pm, with particles larger than 30 pm being extremely rare. Most of the platinum group minerals occur in association with the base metal sulfides and silicates. It is only the mineral laurite which exhibits a preferred association with the chromite grains. Both the grain size and associations are extremely important as these affect the metallurgical behaviour during subsequent processing.

The mine is in the province of North West, 25 km north of the town of Rustenburg. It forms part of the Western Limb of the Bushveld complex and operates under a mining right covering 87 square kilometres.

Current mine infrastructure consists of two decline shafts, namely North shaft and South shaft, and a concentrator.

Both shafts have intersected the reef at the 700-metre level. The primary reef mined at BRPM is the Merensky reef with limited mining of the UG2 reef at both the North and South shafts. The mining method at BRPM is conventional breast stoping with strike pillars. The operating depth for current workings is between 50 metres and 500 metres below surface.

The capacity of the Bafokeng Rasimone Platinum Mine (BRPM) concentrator, originally designed to receive Merensky ore from BRPM’s two decline shafts, with a design capacity of 200 000 tonnes a month, is being upgraded to accommodate production from the Styldrift Mine.

The concentrator follows a traditional MF2 process and includes a conventional three stage crushing process prior to milling and flotation.

The flotation process produces a platinum rich concentrate which is collected and sold as a final product by BRPM for further processing and refining. RBPlat has an offtake agreement with Rustenburg Refineries for the sale of the BRPM JV concentrate.

The concentrator can be described as a robust maintenance intensive environment. In essence the existing concentrator produces 2.7 tonnes of saleable product from every 100 tonnes of virgin rock processed.