Most soils are composed primarily of minerals, although they often also contain organic materials, especially near the surface where vegetation and its decayed products can be incorporated into soil. Soils are often described in terms of a soil profile which extends from the surface downwards until rock is encountered. The profile often grades from unweathered rock at the base, into weathered rock (saprolite) and then into the soil profile, which is often developed as series of horizons. Mineralogy, especially clay mineralogy, often changes from one layer in the profile to the next.
The mineralogical composition of soils can now be determined accurately by full pattern fitting XRPD methods. Often the clay mineralogy of soils is studied in some detail using a variety of instrumental techniques. Ancillary treatments such as removal of organic matter or iron oxides are often required for the analysis of soils. We also have access to the largest grouping of soil scientists in the UK, many of whom specialise in other aspects of soil analysis.