Clay minerals were initially defined on the basis of their crystal size. They were determined as the minerals whose particle diameters were less than 2 μm. This limit was imposed by the use of the petrographic microscope where the smallest particle which could be distinguished optically was of this size. Clays were essentially those minerals which could not be dealt with in a conventional nineteenth century manner. Chemical analyses were nevertheless made of fine grain size materials, most often with good results. However, the crystal structure and mineralogical family were only poorly understood. This was mainly due to the impurities present in clay aggregates, either as other phases or in multiphase assemblages. Slow progress was made in the early twentieth century, but the advent of reliable X-ray diffractometers allowed one to distinguish between the different mineral species found in the <2 μm grain size fraction. Today we know much more about clay mineral XRD (X-ray diffraction) properties; perhaps too much at times.
KeywordsQuartz Magnesium Dust Hydrated Sandstone
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- Barrer RM, Tinker PB (1984) Clay minerals: their structure behaviour and use. Proceeding of the Royal Society, London, 432 ppGoogle Scholar
- Grim RE (1968) Clay mineralogy. Harper and Row, New York, 254 ppGoogle Scholar
- Newman ACD (ed) (1987) Chemistry of clays and clay minerals. Mineralogical Society of Great Britain, Monograph 6, Longmans, London, 480 ppGoogle Scholar
- Velde B (1985) Clay minerals: a physico-chemical explanation of their occurrence. Elsevier, Amsterdam, 423 ppGoogle Scholar
- Velde B (1992) Introduction to clay minerals. Chapman Hall, London 193 pp Weaver CE (1989) Clays, muds and shales. Elsevier, Amsterdam, 819 ppGoogle Scholar