The Basal Reef is the predominant gold-bearing reef at Bambanani. The Steyn facies of the Basal Reef covers approximately 90% of Bambanani’s mining lease area of and overlays, with a very slight angular sub-conformity, the UF1 quartzite of the Welkom Formation. It is overlain by the Khaki Shale unit of the Harmony Formation in the north, but to the south it is overlain by the younger Waxy-Brown Leader Quartzite which erodes the Khaki Shale. Decisions to undercut the Basal Reef may be influenced by the presence and thickness of the Khaki Shale. Thickness of the reef may vary from a few centimetres to over 10m, but it is typically between 1m and 3m thick.

The Stuirmanspan Fault in the west and the De Bron-Vermeulenskraal Fault system in the east bound the Basal Reef at Bambanani Mine. Both are northward striking dextral extensional faults, with significant westerly downthrows. The reef dips easterly and varies from 25 degrees in the west to 45 degrees in the east, or through local deformation against fault can lead to vertical reefs in places. Smaller faults break up the reef but are generally sub parallel to the main structures.

Bambanani has two surface shafts (the East and West shafts). Mining is conducted to a depth of 2365m. Activities at the mine focus on the Basal Reef.

Bambanani is in the final stages of its life of mine and mining is limited to the extraction of the shaft pillar. Mining of the shaft pillar is focused on mini longwalls on the north side and centre of the pillar, separated by safety pillars left along designated main geological structures. Ore transport is through a decline system, stretching from 58 to 75 levels, situated on the northern side of the shaft pillar, to Bambanani West, where hoisting takes place.

Most of the panels are mined on undercut, leaving a reef beam of approximately 80cm in the hangingwall in order to build a beam to support the shale. The challenge remains to control the stoping width and the stability of the beam in a highly fractured and faulted environment, with sill intrusions, weak waxy brown quartzite hangingwall above the shale, complicated by ball and pillow formations.

Backfill has been successfully introduced in all of the panels. The quality of installation has improved drastically as the crew has gained knowledge and understanding of the underground application. The focus will now be to improve the amount of backfill placed vs square metres mined, as well to focus on quality control which will include regular testing of the backfill product.

Bambanani does not have its own mineral processing plant and the mine’s ore is transported by rail for 7km to the Harmony 1 plant for processing.