Sedimentary rocks Clastic sedimentary rocks consist of rock and mineral grains derived from the chemical and mechanical breakdown (weathering) of pre-existing rock. They contain rock fragments and more commonly, particles of quartz and feldspar. Clastic rocks are further classified on the basis of grain size. Underneath each rock type, the Wentworth Scale of particle sizes is shown. Conglomerates (> 2mm) consolidated gravel Boulder (>256mm) Cobble (65-256 mm) Pebble (4-64 mm) Granule (2-4 mm) Sandstones (0.062-2 mm) consolidated sand Very coarse (1.0 - 2.0 mm) Coarse (0.5 - 1 mm) Medium (0.25 - 0.5 mm) Fine (0.125 - 0.25 mm) Very fine (0.0625 - 0.125 mm) Shales (
Posted on: Fri, 05 Jul 2013 19:02:02 +0000
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