About the Mineralogy Laboratory and Clay Research in New Zealand
The Mineralogy Laboratory was established some 50 years ago in the Soil Bureau, DSIR, Lower Hutt. The Laboratory is now housed at the Massey University campus of Landcare Research in Palmerston North. The emphasis has been on characterising clays and clay minerals in soils for agriculture. However, we can also analyse a wide range of other materials, such as clay minerals in sediments, rocks, animal calculi, and building materials.
New Zealand provides a unique environment for earth sciences in general, but especially for soil research. The behaviour and properties of New Zealand soils are closely related to the nature of their mineral constituents. Among these, the clay minerals and associated phases are the most important because of their small particle size, peculiar charge characteristics, and extensive surface area. Thus, a teaspoonful of clay-size (<0.002 mm) minerals can expose a surface area equivalent to that of a football field! The clay mineralogy of soil therefore has a controlling influence on many soil processes, such as water infiltration, swelling/shrinkage, nutrient/heavy metal retention, organic matter stability, and organic pollutant mobility.
The Mineralogical Laboratory has gained an international reputation as a centre of excellence as attested in 2004 by the award to B.K.G. Theng of the Bailey Distinguished Membership from the Clay Minerals Society (USA).
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 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).
Bibliography
Childs, C.W.; Inoue, K.; Seyama, H.; Soma, M.; Theng, B.K.G.; Yuan, G. 1997: X-ray photoelectron spectroscopic characterization of Silica Springs allophane. Clay Minerals 32: 565–572.
Coyne, L.M.; Costanzo, P.M; Theng, B.K.G. 1989: Luminescence and electron spin resonance studies of relationships between O-centres and structural iron in natural and synthetically hydrated kaolinites. Clay Minerals 24: 671–693.
Parfitt, R.L. 1990: Allophane in New Zealand – A Review. Australian Journal of Soil Research 28: 343–360.
Soma, M.; Churchman, G.J.; Theng, B.K.G. 1992: X-ray photoelectron spectroscopic analysis of halloysites with different composition and particle morphology. Clay Minerals 27: 413–421.
Soma, H.; Seyama, H.; Yoshinaga, N.; Theng, B.K.G.; Childs, C.W. 1996: Bonding state of silicon in natural ferrihydrites by X-ray photoelectron spectroscopy. Clay Science 9: 385–391.
Theng, B.K.G. 1974: The chemistry of clay-organic reactions. London, Adam Hilger/New York, John Wiley. 343 p.
Theng, B.K.G., 1979: Formation and properties of clay-polymer complexes. Amsterdam/Oxford/New York, Elsevier Scientific Publishing Company. 362 p.
Theng, B.; Churchman, J. 1993: Taita research centre – four decades of science, 1951-93. Mineralogy. NZ Soil News 41: 123–127.
Theng, B.K.G.; Wells, N. 1995: The flow characteristics of halloysite suspensions. Clay Minerals, 30: 99–106.
Theng, B.K.G.; Russell, M.; Churchman, G.J.; Parfitt, R.L. 1982: Surface properties of allophane, halloysite, and imogolite. Clays and Clay Minerals 30: 143–149.
Whitton, J.S.; Churchman, G.J. 1987: Standard methods for mineral analysis of soil survey samples for characterisation and classification in NZ Soil Bureau. NZ Soil Bureau Scientific Report 79. Lower Hutt, New Zealand, NZ Soil Bureau. 27 p.