ABSTRACT
X-ray diffraction (XRD) remains the main technique for identification of soil clays. XRD, while the main identification technique for crystalline minerals, is unsuitable for poorly crystalline or nanocrystalline minerals such as allophane and ferrihydrite. Electron microscopy is one of the most widely used techniques for identifying and characterising clays, including soil clays. Many studies of soil clays include electron micrographs of the clays, from transmission and/or scanning electron microscopy. Accurate quantitative analyses by all techniques founder on the problem that minerals in soils are different from those in ‘pure’ mono-mineral deposits. Analyses are most reliable when the soils or soil clays form a series, for example a chronosequence, or when examining the effect of a particular treatment on a soil or its clays. The procedure involves correlating the mid-infrared or near-infrared spectra of whole soils with their chemical and physical properties in training sets appropriate for the soils under analysis.
