Jobs at Black Rock Mine Operations (BRMO)

The Nchwaning and Gloria mines make up the Black Rock Mine complex.

The Nchwaning II main drive North system and Nchwaning III satellite tip 2 system were put into operation in September 2022, while the Gloria surface plant and underground silo system, as well as its conveyors, were successfully commissioned in October 2021 and May 2022, respectively. The aim is to increase production at Black Rock Mine to 4.6 million tonnes of saleable product annually by 2025.

African Rainbow Minerals Ltd (ARM) holds a 50% stake in Assmang (Pty) Ltd, while the other 50% is owned by Assore (Pty) Ltd. Assmang is jointly managed by ARM and Assore, with ARM providing administrative and technical services and Assore handling sales and marketing.

The manganese ores in the Kalahari Manganese Field are found within the Hotazel Formation of the Postmasburg Group of the Griqualand West Sequence, which is a sub-division of the Proterozoic Transvaal Supergroup. This sequence is composed of a basal dolomite and banded ironstones and includes the Ghaap, Postmasburg, and Olifantshoek Groups. The Postmasburg Group is made up of basal basaltic andesites of the Ongeluk lava and manganese and banded ironstone of the Hotazel Formation.

The Hotazel Formation, along with the Mapedi shales and Lucknow quartzite sequences above it, have been duplicated by thrusting on the Belgravia, Santoy, and Nchwaning farms. The thrusted orebodies were initially mined at the discovery outcrop of the Kalahari Manganese Field, the Black Rock Koppie, and at the interconnected Belgravia 1 and Belgravia 2 shafts. Mining reached depths of around 200 meters. The manganese resources hosted in these thrusted orebodies are collectively referred to as the Black Rock (Koppie area) orebodies. The average thickness of the Hotazel Formation is roughly 75 meters, and the manganese orebodies within it occur as three stratabound and stratiform units of varying thicknesses. Seam 1, the lowest orebody, has a higher grade compared to the topmost orebody (Seam 2), while Seam 3, located in between, is thin and uneconomic.

The Bord and Pillar mining method is employed, using trackless mechanized equipment. Two manganese seams are mined, with Seam 1 at Nchwaning 3 being up to 6 meters thick and up to 5 meters being mined to minimize dilution. Nchwaning Seam 2 is mined with an optimum cut of 4.0 meters. Gloria Seam 1 is approximately 14 meters thick, but only an optimum cut of 4.2 meters is mined. No mining has been conducted on Gloria Seam 2 so far.

Mining in the eastern part of Nchwaning occurs at a depth of 200 meters, while the deepest excavations currently reach 570 meters below the surface. Ore from Nchwaning No 2 Mine is crushed underground before being transported to a surface stockpile through a vertical shaft. Similarly, ore from Nchwaning No 3 Mine is crushed underground and conveyed to a surface stockpile through a decline conveyor system.