Methods
Imogolite – an amorphous soil mineral commonly formed from volcanic parent materials. Image - N Yoshinga
Information about routine sample preparation and analysis methods.
X-ray diffractometry (XRD)
X-ray diffractometry (XRD) remains the standard technique for identifying and quantifying clay minerals. This technique is often applied in conjunction with differential thermal analysis (DTA) and transmission electron microscopy (TEM).
Wet chemical (selective dissolution) and surface analytical methods
Wet chemical (selective dissolution) and surface analytical methods are useful for characterising poorly crystallised (short-range order) layer silicates, such as allophane and ferrihydrite that do not give well-defined XRD peaks (Parfitt 1990; Soma et al. 1996; Childs et al. 1997). All these techniques are available or accessible at Landcare Research, Palmerston North. In most instances, samples must be chemically treated before instrumental analysis is applied. This is because clay particles in soil, sediment, and rock are commonly associated with, and cemented by, other substances notably carbonates, iron oxides/hydroxides, and organic matter. For this reason, fundamental investigations on the surface- and colloid-chemical properties of clay minerals have, in the main, been carried out using purified materials from geological deposits or synthetic clay minerals (Theng 1974, 1979; Theng et al. 1982; Coyne et al. 1989; Soma et al. 1992; Theng & Wells 1995).