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'''Shale''', sometimes called ''Mudstone'' is a smooth fine-grained [[sedimentary rock]] often used to make made from clay or mud. Shale is the most common type of sedimentary rock, and a large proportion of [[chalkboardfossils]]sare found in it. Shale can be converted into slate by the application of heat and pressure, which is used in building construction, and for a number of other useful items such as chalk boards.