Driefontein is a deep level underground gold mine located along the northern and southwestern margins of the Witwatersrand Basin in South Africa. This mine is typical of the many Witwatersrand Basin operations, which have been the primary contributors to South Africa’s production of a significant portion of the world’s recorded gold output since 1886.

The orebodies at Driefontein are laterally continuous with relatively long-range predictability. This lends to clear patterns of mineralisation governed by sedimentary characteristics.

The principle mining at Driefontein takes place on the Multiband Carbon Leader Reef. In most cases, the reef was deposited along a structurally controlled basin edge, which created discrete unconformable surfaces of deposition. This led to typical main channel, wide reef packages, which are generally >2m thick and bottom loaded.

The Witwatersrand Basin comprises a 6,000-meter vertical thickness of sedimentary rocks, extending laterally for some 350 kilometres northeast to southwest by some 120 kilometres northwest to southeast, generally dipping at shallow angles toward the centre of the Witwatersrand Basin. The Witwatersrand Basin outcrops at its northern extent near Johannesburg, but to the west, south and east it is overlaid by up to 4,000 meters of volcanic and sedimentary rocks. The Witwatersrand Basin is Archaean in age, meaning the sedimentary rocks are of the order of 2.8 billion years old.

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Driefontein is a large, well established, intermediate to ultra-deep level gold mine typical to similar mines on the far West Rand mining narrow tabular ore bodies. It has been in production since the 1950s with the last shafts being commissioned in the late 1990s. It includes all the permanent infrastructure required to access and mine the underground areas. All the mineral processing infrastructure is also well established and in use.

Driefontein consists of four operating shafts, No. 1, No. 4, No. 5, and No. 8 Shafts. The deposit is accessed from surface using shaft systems down to 50 Level (the lowest working level) at No. 5 Shaft, approximately 3,300m below surface.

The shafts are well maintained and will support mining operations over the LoM. The underground development is extensive, as can be expected of a mature mine of this size. All footwall access development is mined using mechanical rail-bound methods that are well understood. All stoping is completed using conventional, narrow tabular methods and as such is relatively labour intensive.

The four producing shaft systems mine various contributions from pillars and open ground. No. 2 Shaft is being used solely for hoisting purposes and a further two are being utilised for pumping. Some of the older shafts are on care-and-maintenance and have been planned for closure in 2022 following a footprint optimisation project to contain costs.

Mining method:
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Driefontein has three metallurgical plants exploiting the Carbon Leader Reef, the Ventersdorp Contact Reef and the Middelvlei Reef.

The Driefontein 1 Plant treats underground ore and has a processing capacity of 240,000tpm. The upgraded CIP circuit at the No 1 Plant consists of a semi-autogenous grinding (SAG) mill circuit followed by cyanide leaching, CIP and a central elution facility.

The Driefontein 2 Plant processes SRD material, which is delivered by rail and truck. Plant flow incorporates two SAG mills and a ball milling circuit, cyanide leaching and a CIP plant. A CIL circuit was commissioned in 2014 at the No 2 Plant to improve recoveries by replacing the aging CIP circuit.

The Driefontein 3 Plant was originally designed as a uranium plant but was converted to process low-grade surface rock in 1998. Similar to the No 2 Plant, SRD ore is delivered by rail and truck. The plant has four SAG mills followed by cyanide leaching and a CIP circuit.