The mineral assets are historical gold plant tailings material from the mining of auriferous and uraniferous ore from the goldbearing, late Archaean (2.7Ga to 3.2Ga), Witwatersrand Basin in the West Rand Goldfield. The typical composition is quartz (70% to 80%), mica (10%), chlorite and chloritoid (9% to 18%) and pyrite (1% to 2%). Gold, uranium oxide, zirconium and chromium are minor constituents.

The composition of a TSF depends on the geochemical make-up of the material being mined and the chemicals used in the mining and extraction process. Further, the internal structure of the TSF reflects the mining strategy and depositional methodologies employed for each operation. The bulk density of tailings material and the lateral and vertical variation in moisture content is a critical factor in the accurate estimation of tonnages. In addition, secondary processes such as metal remobilisation, erosion, weathering, leaching and acid mine drainage can affect the geochemical characteristics of a TSF. Gold can undergo mobilisation within the TSF over time, and hence, may exhibit areas of reconcentration, and even be present in the sub-structure (footprint) soil. These factors can result in a considerable variation in gold content and distribution throughout the TSF and such variation has an impact on final recoveries and projected revenues for the operation.

Tailings from Cooke plant (RSO) are deposited into historic, dormant, unrehabilitated opencasts connected to the old underground workings of the Randfontein Estates operation as part of an approved EMPR. An estimated 11.1Mt of depositional capacity is available in these pits assuming no further storage capacity in the connected underground workings. To date however, there is no indication that the tailings are beginning to beach and the material is still filling the underground voids.

A total of 4.0Mt of depositional capacity is still available at the Cooke 4 (Ezulwini) TSF complex.

There is sufficient capacity for depositing the three-year LoM residue tailings material.

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.

Cooke has four vertical shaft complexes (including one with a sub-shaft) and two mineral processing plants.

All four shafts are currently only used for dewatering.

Mining methods:
• Mining of the TSF is via hydro (waterjet) methods;
• Mining of SRD with LHD trucks.

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.

The Cooke plant treats TSF material from the RSO and is toll treating some minor quantities of SRD material from third parties.

Ezulwini plant is toll treating SRD material from third parties and the Kloof operation.

The Ezulwini plant has an integrated uranium extraction circuit which has been used in the past to extract uranium from Middle Elsburg ore, but which is currently dormant.