The Grootegeluk Formation of the Waterberg Coalfield is about 70 m thick and consists of relatively thin coal beds interbedded with numerous mudstone and carbonaceous mudstone layers, Maceral analyses of the coal seams and the interbedded carbonaceous mudstones show that vitrinite is the dominant maceral (up to 90 vol%), whereas inertinite, liptinite and reactive semifusinite generally occur in minor proportions. The vitrinite content increases upward in the formation, with a concomitant decrease in inertinite (including reactive semifusinite) from around 60% inertinite at the base of the formation. The upward increase in the vitrinite concentration is associated with an increase in the energy of the depositional environment, which is also considered to have been instrumental in the enhanced preservation of the vitrinite. The repetitive nature of the coal-mudstone succession, the lateral persistence of cycles, and the maceral and ash proportions, indicate that the formation may have resulted from a combination of allogenic controls (tectonism and climate) and authigenic controls (environments of deposition). The vitrinite reflectance ((R) over bar max) of the Grootegeluk Formation (mean 0.72%) and palynological evidence indicate that the Grootegeluk Formation was subjected to maximum post-depositional temperatures of about 100 degrees C. The lower portion of the Grootegeluk Formation is dominated by kaolinite, quartz and minor amounts of apatite, and the upper parts by quartz, kaolinite and minor amounts of montmorillonite, illite and microcline. The base of the Grootegeluk Formation is considered to have been relatively more distal and the upper portions more proximal to the source of the sediments, At the base of the Grootegeluk Formation a similar to 2 m thick tonstein zone occurs, which is dominated by well-crystallised kaolinite, organic matter ( similar to 40 wt%), siderite, calcite and minor proportions of apatite, The tonstein zone has mineralogical, maceral and chemical characteristics distinctive from the other mudstones.