Mining takes place in a structurally complex zone between two major north-south trending faults the De Bron/Homestead Fault in the west and the Saaiplaas Fault in the east. The ore body has been subjected to severe deformation and contains numerous folds (anticlines and synclines) as well as an abundance of smaller faults.

The dip of the reef bands is very variable from 45 degrees to the east, adjacent the western side of the lease, to less than 2 degrees in parts of the southern area.

Production is hosted within two quartz pebble conglomerate bodies, developed above unconformity surfaces, termed reefs. These two reefs are known as the Basal and “B” reefs. Approximately 80% of the centares (1 centare = 1 square metre) are from the Basal Reef horizon and 20% from the “B” Reef horizon.

The Masimong complex comprises an operating shaft (5 shaft) and 4 shaft, which, although closed for mining, is used for ventilation, pumping and as a second escape outlet. Masimong exploits the Basal Reef and the B-Reef by means of conventional tabular narrow reef stoping method. Mining is conducted at a depth of between 1 650m and 2 010m below collar.[OPERATIONAL PERFORMANCE 2019. P.25]

Masimong mines at moderate depths of between 1 650m and 2 010m below surface. The reef horizon is accessed by means of conventional grid development. The economic reef horizons extracted are the Basal Reef and the B Reef. Basal Reef accounts for approximately 80% of the on-reef production profile, and is mined on open and undercut operations, depending on whether the reef is overlain by shale. B Reef mining makes up the remaining 20% of the on reef production profile. It is located approximately 120m stratigraphically above the Basal Reef, thus necessitating separate infrastructure (i.e. footwall development). The presence of the upper shale marker approximately 20m thick below the B Reef strains the development rates of the B Reef, requiring drop raising to be done to effect holing on all box holes. Also all on-reef development needs to be done by means of wide raising. Despite the marginality of the ore body and the current economic environment, reserves on the mine give a life expectancy of four years, mainly due to the successful opening of known value trend extensions.

The ore mined is transported by rail for processing at the Harmony One carbon-in-pulp plant, situated some 12km from the shaft. [MINERAL RESOURCES AND MINERAL RESERVES 2019. P. 101]

The ore is taken up the slow-moving conveyers from underneath the silos and discharged directly into the feed hopper for the six fully autogenous mills. For control purposes the mill feed belts and the mill discharge pumps both have variable speed drives. Each mill is a closed circuit with a 1200mm primary cyclone with mass flow measurement on the feed. The primary cyclone overflow is screened on a 600µm linear screen for the removal of coarse woodchips and tramp steel.

Calcium Oxide (lime) is added to the 6 thickeners (operating in 3 parallel modules) as slaked lime with levels of CaO being controlled at between 0.014 and 0.016% CaO. The lime maintains a protective level of alkalinity in the leach section to prevent the generation of poisonous HCN (cyanide) gas in the process. Thicken ........