The coal measures of the North Block Complex occur on the eastern edge of the Witbank coalfield, within the Permian-age Vryheid formation of the Ecca Group in the Karoo Sequence. The Witbank coalfield is situated in the northern part of the Main Karoo basin and extends about 190km west-east between Brakpan and Belfast and about 60km north-south between Middelburg and Ermelo.

The main Karoo Basin:
- Was filled between the Late Carboniferous and Middle Jurassic periods;
- It is lithostratigraphically subdivided into the Dwyka, Ecca and Beaufort Groups, succeeded by the Molteno, Elliot and Clarens Formations and the Drakensburg Formation (volcanics);
- The coal bearing Ecca Group has been divided into three sub-units: the Pietermaritzburg; Vryheid and Volksrust Formations.

The Witbank Coalfield:
- The coal-bearing Vryheid Formation attains a thickness of 70m to 200m in the Witbank Coalfield;
- Here the Vryheid Formation consists of five coarsening-upward sequences with coal seams associated predominantly with the coarser grained fluvial facies at the top of each sequence;
- The No. 5, 4, 2 and 1 coal seams are of economic interest.

Strathrae’s surface operation mines the No.2 Seam using the truck and shovel mining method. ROM coal from the underground operations is transported to the plant by a conveyor belt. The thermal coal and high grade coal plants each have a capacity of 300tph. Strathrae’s plant, with 130ktpm capacity, is a beneficiation plant producing export quality coal.