Oxides of iron accumulate through weathering and colour many soils - uniformly if the conditions are well drained and aerated. The red colour of hematite signifies conditions that are warmer, drier, and less affected by organic matter than those indicated by the yellowbrown colour of goethite. Hematite is the stronger of the two pigments and many red soils contain more goethite than hematite.
Some soils have an upper yellow-brown and a lower red B horizon. In the former, organic matter and redox conditions have preferentially removed the hematite. Most humic soils have an oxidic subsurface horizon but oxidic soils are not necessarily highly weathered and may be found over a wide spectrum of climatic conditions (Soil forms: Pinedene, Griffin, Clovelly, Bloemdal, Hutton, Shortlands).