Merensky Reef

The Merensky Reef is a layer of igneous rock in the Bushveld Igneous Complex (BIC) in the North West, Limpopo, Gauteng and Mpumalanga provinces of South Africa which together with an underlying layer, the Upper Group 2 Reef (UG2), contains most of the world's known reserves of platinum group metals (PGMs) or platinum group elements (PGEs)—platinum, palladium, rhodium, ruthenium, iridium and osmium.

[1] The composition consists predominantly of cumulate rocks, including leuconorite, anorthosite, chromitite, and melanorite.

[5] The Merensky Reef is similar to the Platreef because of the presence of primitive mantle, layered intrusions and levels of nickel and copper.

The first accepted hypothesis of the Merensky Reef suggests the chromite crystallization originated from hybrid melts and significant lateral mixing of new and resident magma.

[6] In detail, the first hypothesis suggests the high of PGE concentrations were a result from the sulfide and silicate melt.

[7] The initial recovery of platinum in South Africa took place on several of the large East Rand gold mines and the first separate platinum mine was a short lived venture near Naboomspruit that worked very patchy quartz reefs.

The discovery of the Bushveld Igneous Complex deposits was made in 1924 by a Lydenburg district farmer, A F Lombaard.

[2][10] This was an alluvial deposit but its importance was recognized by Hans Merensky whose prospecting work discovered the primary source in the Bushveld Igneous Complex and traced it for several hundred kilometres by 1930.

[4] Extensive mining of the Reef didn't take place until an upsurge in the demand for platinum group metals used in exhaust pollution control in the 1950s, made exploitation economically feasible.