 clay minerals are hydrous aluminium phyllosilicates, sometimes with variable amounts of iron, magnesium, alkali metals, alkaline earths, and other cations found on or near some planetary surfaces. clay minerals form in the presence of waterhttp://www.clays.org/journal/archive/volume%201/1-1-19.pdf and have been important to life, and many theories of abiogenesis involve them. they have been useful to humans since ancient times in agriculture and manufacturing. == properties == clays form flat hexagonal sheets similar to the micas. clay minerals are common weathering products (including weathering of feldspar) and low temperature hydrothermal alteration products. clay minerals are very common in fine grained sedimentary rocks such as shale, mudstone, and siltstone and in fine grained metamorphic slate and phyllite. clay minerals are usually (but not necessarily) ultrafine-grained (normally considered to be less than 2 micrometres in size on standard particle size classifications) and so may require special analytical techniques for their identification/study. these include x-ray diffraction, electron diffraction methods, various spectroscopic methods such as mÃ¶ssbauer spectroscopy, infrared spectroscopy, raman spectroscopy, and sem-eds or automated mineralogy solutions. these methods can be augmented by polarized light microscopy, a traditional technique establishing fundamental occurrences or petrologic relationships. == occurrence == given the requirement of water, clay minerals are relatively rare in the solar system, though occur extensively on earth where water has interacted with other minerals and organic matter. clay minerals have been detected at several locations on marsclays on mars: more plentiful than expected science daily. dec. 20, 2012 including echus chasma and mawrth vallis and the memnonia quadrangle and the elysium quadrangle. spectrography has confirmed their presence on ceresa.s. rivkina, e.l. volquardsenb, b.e. clark. 'the surface composition of ceres: discovery of carbonates and iron-rich clays' and europa.http://www.nasa.gov/jpl/news/europa-clay-like-minerals-20131211.html == classification == clay minerals can be classified as 1:1 or 2:1, this originates from the fact that they are fundamentally built of tetrahedral silicate sheets and octahedral hydroxide sheets, as described in the structure section below. a 1:1 clay would consist of one tetrahedral sheet and one octahedral sheet, and examples would be kaolinite and serpentine. a 2:1 clay cons
Clay_minerals_group Phyllosilicates Soil_chemistry