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Clay minerals are very common in soils, in fine-grained sedimentary rocks such as shale, mudstone, and siltstone and in fine-grained metamorphic slate and phyllite. [ 9 ] Given the requirement of water, clay minerals are relatively rare in the Solar System , though they occur extensively on Earth where water has interacted with other minerals ...
Clay is a type of fine-grained natural soil material containing clay minerals [1] (hydrous aluminium phyllosilicates, e.g. kaolinite, Al 2 Si 2 O 5 4). Most pure clay minerals are white or light-coloured, but natural clays show a variety of colours from impurities, such as a reddish or brownish colour from small amounts of iron oxide .
Other earth materials include soil blocks typically stabilized with a cement additive and produced with forms or compression. Rammed Earth consists of walls made from moist, sandy soil, or stabilized soil, which is tamped into form work. Walls are a minimum of 12″ thick. Soils should contain about 30% clay and 70% sand. [4]
The soil texture is determined by the relative proportions of the individual particles of sand, silt, and clay that make up the soil. A soil texture triangle plot is a visual representation of the proportions of sand, silt, and clay in a soil sample.
World War II pillbox on eroding boulder clay, Filey Bay, England Boulder clay cliffs in Gwynedd with Dinas Dinlle in the background. Boulder clay is an unsorted agglomeration of clastic sediment that is unstratified and structureless and contains gravel of various sizes, shapes, and compositions distributed at random in a fine-grained matrix.
The British Geological Survey describe the Wadhurst Clay Formation as made of soft, dark grey thinly-bedded mudstones ("shales") and mudstones with subordinate beds of pale grey siltstone, fine-grained sandstone, shelly limestone, clay ironstone and rare pebble beds, which shows evidence of unconformable weathering at the top of the bed. [12]
In turn, rocks that possess clay as the majority particle are called claystones. In geology, a mixture of both silt and clay is called mud. Rocks that possess large amounts of both clay and silt are called mudstones. In some cases the term shale is also used to refer to mudrocks and is still widely accepted by most.
In order for a rock to be considered a claystone, it must consist of at least fifty percent clay (phyllosilicates), whose particle measures less than 1/256 of a millimeter in size. Clay minerals are integral to mudrocks, and represent the first or second most abundant constituent by volume. They make muds cohesive and plastic, or able to flow.