Name: Doornkop mine.

Location: The Doornkop mine is located about 30 km west of Johannesburg, on the northern rim of the Witwatersrand basin, in South Africa.

Controlling Company: Harmony Gold Mining Company.

Brief Description: Doornkop is a single-shaft operation.  The operation focuses on narrow-reef conventional mining of the South reef. Ore from the operation is processed at the Doornkop plant. It has a life-of-mine of 17 years.

Brief History: Exploration in the Doornkop area started in the early 1930s, with sinking of the main and ventilation shafts beginning in 1983 by JCI. By 1989, steady production had been achieved from the Kimberly reef, which is shallower than the South reef that is currently being mined. The deepening of the South reef shaft was approved in October 1991, with the reef being intersected in October 1993. Stoping of the South reef began in 1995. Shaft deepening continued with stoppages from November 1996 to May 1999. Harmony acquired Doornkop in January 2000. The South reef project was relaunched in January 2003, resulting in the deepening of the mine to 1 980 m below collar. 
Mining of the Kimberley reef was suspended during the 2014 financial year to focus on the build-up of mining of the South reef and to prevent losses resulting from the lower gold price. 

Products: Gold.

Geology/Mineralisation: The Doornkop shaft lease area is bounded by and lies to the south-east of the major north-easterly striking Roodepoort fault, which dips to the south and constitutes the southern edge of the Witpoortjie horst block or gap. This horst block comprises the stratigraphically older sediments of the West Rand Group, the overlying Central Rand Group sediments having been removed by erosion. Several other faults, constituting and lying south-east of the Roodepoort fault, including the Saxon fault, also comprise conspicuous structural breaks. A second 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. 

Virtually the entire upper Witwatersrand section is present in the lease area and therefore all the major zones are present, however, owing to 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 Kimberly reef are considered viable at this stage. 

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

Owing to the limited geological information, one of the biggest risks for the operation has been the intersection of any geological structures, which may have a significant change in the reef elevations that can result in some of the resources ending up below infrastructure, rendering it inaccessible from current levels with a potential to negatively affect the declared reserves. To curb this hazard, an extensive exploration drilling programme from underground platforms and using long incline borehole machines has been started, which will lead to fewer geological surprises and/or changes in mine design. A recently completed seismic survey will also help with geological understanding of the regional structure and reef elevations in the major blocks. Structural interpretation of the seismic survey information has begun and all changes will be reflected in the coming year’s geological interpretation and life-of-mine designs. 

Reserves: Total proven and probable reserves as at June 30, 2017, were estimated at 4.6-million tonnes grading 4.96 g/t gold.

Resources: Total mineral resources as at June 30, 2017, were estimated at 17.1-million tonnes grading 7.86 g/t gold

Mining Method: Narrow reef conventional mining of the South reef.

Major Infrastructure and Equipment: Doornkop’s surface and underground infrastructure, including its power and water supplies, can handle current planned peak production level requirements. The 192, 197 and 202 levels are track bound while current development on 207 and 212 levels is trackless, with plans in place to eventually make these levels track bound. Work continues on certain essential underground infrastructure on the South reef, including the permanent tipping arrangements required to make the 207 and 212 full production levels. Ore is hoisted through the main shaft. Currently, the mine uses Sibanye’s Cooke 1 shaft, which is 7 km away, as a second escape way. 

The Doornkop mine features a carbon-in-pulp plant, with a milling capacity of 225 000 t/m. This includes about 120 000 t/m of ore from Sibanye’s Cooke operations, which is toll treated at Doornkop.

Prospects: Increased confidence levels and more accurate geological modelling, with better defined production levels based on the seismic survey and drilling conducted are envisaged.

Contact: Investor relations manager Lauren Fourie.

Contact Details:
Harmony
Tel +27 11 411 2000
Fax +27 11 692 3879
Email HarmonyIR@harmony.co.za
Website https://www.harmony.co.za