under laboratory conditions may react and behave differently from its bulky coun-
terpart. Issues of heterogeneity aside, minor constituents in clays and the scale and
conditions of testing can give rise to discrep ancies in the results of measurements
carried out in different laboratories. A variety of spectr oscopic and instrumental
techniques have been used to analyse and characterize clays and clay minerals.
Improvements in sensitivity, selectivity, and accuracy are constantly being sought.
The development of new techniques and the refinement of old ones create a complex,
multidimensional problem. Verification of the reproducibility of results, obtained in
different laboratories, is not an option but a necessity. The chemical and mineral
composition of clays is more difficult to quantify than other hard rocks. Differences
in clay mineral populations, structural imperfections, variations in crystallinity, and
the presence of impurities are problems that are specifically associated with the
identification and quantitative analysis of clays.
Experimenting with artificial mixtures of clay minerals is popular in soil and
geotechnical testing. Mixtures of clay minerals of different origin would be expected
to behave like natural, multiphase clay material. However, it is difficult, if not im-
possible, to simulate the natural fabric and the intimacy of contact between neigh-
bouring particles formed over geological periods of interaction. Likewise, computer
modelling has become important over the past decade or so. This approach to
research can be rewarding if the model is properly validated, and not used to justify
or prove a preconceived notion.
The different aspects of clays mentioned above refl ect the unique nature of clays
and clay minerals. No other group of inorganic materials have so many specie s, show
such a wide range of reactivity and propensity for modification, or enjoy such a
diversity of practical applications as clay minerals. In addition to their conventional
uses, as in ceramics and paper coating, clays have found many novel applications.
Clay minerals are naturally occurring nanomaterials, abundant, inexpensive, and
environmental friendly. As such, they have a huge potential for the synthesis of clay-
polymer nanocomposites with superior mechanical and thermal properties. The op-
timization of adsorption properties, swelling behaviour, colloidal and rheological
properties, and the design of new types of organo-clays also open prospects of using
clay minerals for pollution control and environmental protection. Many clay
scientists and geotechnical engineers are also aware of the negative side of clays as
manifested in the form of landslides, mudflows, and the deterioration of clay-based
construction materials. In so far as it is impossible to control nature, prevention, and
remediation are the only practical ways of responding to such destructive natural
processes.
Clay science is a multidisciplinary endeavour, combining geology, mineralogy,
crystallography with physics, geotechnology, and soil mechanics together with in-
organic, organic, physical, and c olloid chemistry. The contributions to clay science
of the biological, medical, and pharmaceutical sciences are increasing, and this trend
will continue.
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