Cooke is a shallow to intermediate level (1,150m to 1,390m maximum depths) gold and uranium operation, which has been in production since 1961. Situated in the West Wits Line of the Witwatersrand Basin, near the town of Randfontein.

The principal horizons of the Middle and Upper Elsburgs consists of multiple reefs in a structurally and sedimentologically complex arrangement. The Elsburg Reefs occur in a distinct mineralised sedimentary alluvial fan setting, with closely spaced, multiple reefs in a sub-cropping relationship in the proximal areas.

This “composite nature” of the reefs in the proximal areas, led to these operations originally being mechanised, initially extracting a composite package of conglomerates.

Downdip from the proximal areas, the orebodies at Cooke are laterally continuous with relatively long-range predictability. This lends to clear patterns of mineralisation governed by sedimentary characteristics.

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.

Gold mineralisation occurs within laterally extensive quartz pebble conglomerate beds called reefs, which are developed above unconformable surfaces near the basin margin. As a result of faulting and primary controls on mineralisation processes, the goldfields are not continuous and are characterised by the presence or dominance of different reef units. The reefs are generally less than two meters in thickness and are widely considered to represent laterally extensive braided fluvial deposits or unconfined flow deposits, which formed along the flanks of alluvial fan systems around the edge of an inland sea. Dykes and sills of diabase or dolerite composition are developed within the Witwatersrand Basin and are associated with several intrusive and extrusive events.

Gold generally occurs in native form, often associated with pyrite, carbon and uranium. Pyrite and gold within the reefs display a variety of forms, some obviously indicative of detrital transport within the depositional system and others suggesting crystallisation within the reef itself.

As early as 1923, the presence of uranium was noted in the Witwatersrand reefs. It was found that on average the reefs contain about 0.03% uranium and as a by-product of gold relatively low uranium grades can be recovered. Notwithstanding different opinions as to the origin of the uranium in the reefs, most theories accept localisation of both gold and uranium a function of sedimentary textures. Metal concentrations are directly related to the reefs. Exploration programmes and eventual evaluation of gold and uranium according to a placer philosophy, prove to be highly successful.

The most fundamental controls of gold and uranium distribution are the primary sedimentary features such as facies variation and channel directions. Consequently, the modeling of sedimentary features within the reefs and the correlation of payable grades within certain facies is key to in situ reserve estimation, as well as effective operational mine planning and grade control.

Cooke is a large, established, shallow to intermediate-level gold mine which has been producing gold and uranium since 1961. Cooke underground operations are on care and maintenance.

The surface mining is located in the West Rand District Municipality of the Gauteng province, South Africa. Cooke shafts are located approximately 30km to 40km south-west of Johannesburg. The sites are accessed via the R28 highway between Randfontein and Westonaria or via the N12 national road between Johannesburg and Potchefstroom. The Randfontein Surface Operations (RSO) assets include several TSFs on the West Rand near Randfontein.

The underground mine infrastructure, which is on care and maintenance, consists of four shaft complexes that previously mined open ground and pillars (white areas). Cooke 4, previously operated at 1,634m below surface (58 Level at Cooke 4 SV Shaft) and was declared uneconomical for exploitation from August 2016. Cooke 1, 2 and 3 Shafts have also since been declared non-economical for exploitation. The decision was made to close the underground workings. The principal mining took place on the Middle and Upper Elsburg Reefs. The remainder of the mining took place on the secondary reefs, namely the Kimberly Formations and the VCR. The only production currently is from surface TSF. The production from the four Cooke shafts could be hoisted to surface separately. Underground material from Cooke 1,2 and 3 was previously processed at the Doornkop plant, operated by Harmony Gold Mining Company Ltd (Harmony), on a toll treatment basis. Cooke 4 production and overflow from the Cooke 3 Shaft was treated at Ezulwini along with ore from SRDs on a toll treatment basis.

Mining method:
• Cooke 1,2 and 3: conventional scattered breast mining and pillar extraction
• Hydraulic reclamation (water jets), gravity feed to sump pump station and pumped via pipeline to a processing plant
• Dump, load and haul of SRD.

The Cooke Operations consist of three metallurgical plants.

The Cooke Plant was constructed in 1978 and has a nameplate capacity of 280,000tpm.

In 2005, it was converted from a reef treatment plant to treat sand from the nearby high-grade Dump 20 tailings storage facility (TSF). High grade ore from the Cooke 1, 2 and 3 shafts was diverted for toll treatment at Harmony’s Doornkop Plant. Doornkop is a carbon-in-pulp plant.

Sibanye owns and manages significant extraction and processing facilities at its operations, where gold-bearing ore is treated and processed to produce gold doré.