The Doornkop shaft lease area lies to the south-east of the major north-easterly striking Roodepoort fault, which dips to the south and constitutes the southern Detailed Mineral Resource and Mineral Reserve estimates are presented in this section edge of the Witpoortjie horst block or gap.

This horst block comprises the stratigraphically older sediments of the West Rand Group, with the overlying Central Rand Group sediments having been removed by erosion. Doornkop is bounded by the Roodepoort fault and a number of other faults, including the Saxon fault, which constitute conspicuous structural breaks. Another major fault, the Doornkop fault, which trends in an east-west direction, occurs toward the southern portion of the lease area. This fault dips to the south and has an up-throw to the north.

As nearly the entire upper Witwatersrand section lies within the lease area, all major zones are present. However, given the distance of the area from the primary source of gold, the number of economic bands and their payability is limited. Eight of the well-known reefs are present in the area but only the South Reef and potentially the Kimberley Reef are considered viable at this stage.

The South Reef is between 7.5m and 60m above the Main Reef horizon. The hanging wall of the South Reef consists of siliceous quartzites with non-persistent bands of ‘blue shot’ grit and thin argillite partings. The South Reef footwall is a light coloured and fairly siliceous quartzite. Secondary conglomerate bands and stringers in the hanging wall and footwall of the South Reef may contain sporadic gold values. The general strike of the reef is east-west with a flat dip from 5 to 15 degrees.

Exploration drilling is set to continue in the coming financial year, and will target potential high-grade areas and those with limited geological information, to further increase geological confidence.

Doornkop is a single-shaft operation currently exploiting the South Reef to some 2000m below surface. The narrow South Reef is exploited by means of conventional stoping. Mining of the Kimberley Reef was suspended during FY14 to focus on the build-up of production from the South Reef and to prevent losses as a result of the lower gold price. Mining of the Kimberley Reef may resume should economic circumstances improve sufficiently.

The mining method used is longwall mining with stability pillars on major geological structures. The flat dip, which results in the development of long cross cuts, presents challenges in terms of ore handling, especially for the bottom part of the raises, ventilation and in the long lead times between the start of cross cut development to completion of stoping per raise line.

The gold plant consists of a milling section for grinding of ore, thickeners for dewatering (pulp for leach feed), a leach section for dissolution of gold, using liquid sodium cyanide as one of the reagents, Carbon in Pulp for adsorption of dissolved gold and a recovery section which consists of elution, electro-wining and a smelt house. All tailings are pumped to a Tailings Storage Facility, adjacent to the plant on the northern side.

The Doornkop TSF consists of one active compartment which is raised in the upstream direction. The residue is deposited hydraulically by means of ring feed pipeline to open ended pipe deposition points along the day wall, pool wall including the wing walls both sides of the penstock and into the basin. All supernatant and storm water is decanted off the deposits through a gravity penstock that discharges into a canal draining to the return water dam located east of the TSF. From the return water dam, the water is pumped back to the plant for reuse.