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 on the border of the provinces of Mpumalanga and Limpopo, 25 km west of the town of Burgersfort. It forms part of the Eastern Limb of the Bushveld complex and operates under a mining right covering 140 square kilometres.

The current mine infrastructure consists of two major decline shafts, namely North shaft and South shaft, three adits on Onverwacht Hill and a concentrator. The mine is a hybrid operation using conventional stoping, supported by both trackless development and ore clearance. The mine extracts UG2 reef from surface to 450 metres below surface. The mining method is conventional breast stoping with strike pillars.

Froth flotation is the primary mineral processing separation step employed in the beneficiation of PGM ore bodies. Anglo Platinum operates a significant portion of the total installed flotation capacity in the PGM industry, which is installed at 20 operating plants across the Bushveld.

Anglo Platinum has 20 operating concentrators sited around the Eastern, Northern and Western limbs of the Bushveld complex. The concentrators treat mainly Merensky and UG-2 ores, with Potgietersrust (PPL, Sandsloot) and PPRust North being the only two plants designed to treat the Platreef ore.

For typical UG2 ores, for example, the finer natural PGM grain size in the in situ ore and the relative performance of PGM flotation plants indicate that the ‘watershed’ size where flotation drops off significantly must be relatively fine. This is indicated in, where data collected from a UG2 concentrator illustrate the relative recovery by size fraction in the mainstream roughers and scaven ........