Churchman, G.Singh, M.Marchuk, S.2025-12-172025-12-172018New Zealand Journal of Agricultural Research, 2018; 61(3):340-3460028-82331175-8775https://hdl.handle.net/11541.2/130809Using data from the literature, we pose the question of the extent to which a knowledge of soils is contributed by that of its clay fraction. In the past, soil characteristics have not related well to mineralogical analyses but we have redefined clays and also used a computer programme to more closely analyse X-ray diffraction (XRD) profiles. It was found that cation exchange capacities and specific surface areas of soil kaolinites almost always exceed those of standard kaolinites. The surfaces of soil clays are often coated by organic matter, which reduces their capacity to adsorb dissolved organic carbon (DOC). Oxidised iron is closely associated with phyllosilicate clays and enhances their capacity to adsorb DOC. Computer-aided decomposition of XRD traces show that phyllosilicates may contain several phases and react dynamically with potassium-containing solutions. Clays should be regarded as natural products with as yet undiscovered applications, including for cancer treatment.enCopyright 2018 The Royal Society of New Zealand Access Condition Notes: Accepted manuscript available after 1 April 2019soil claysorganic matteriron oxidesXRD decompositionpotassium dynamicscancer treatmentJournal article10.1080/00288233.2018.14282042-s2.0-85041557093