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Sedimentary Rocks - rocks formed from the hardening and cementing of layers of sediment. Kinds of sedimentary rocks are clastic, chemical and organic. The process of weathering produces sediment —loose particles of rock created by the weathering and erosion of rock, by chemical precipitation from solution in water, or from the secretions of organisms. Sediment is transported and deposited by water, wind, or glaciers. Compaction and cementation transform sediment into solid sedimentary rock. Lithification refers to the processes by which sediments are transformed into solid sedimentary rocks. Clastic sediments are materials that originate and are transported as solid particles derived from weathering. Clastic sedimentary rocks, which are classified by particle size, contain a variety of mineral and rock fragments, with clay minerals and quartz the chief constituents. Common clastic sedimentary rocks include shale (the most common sedimentary rock), sandstone, conglomerate and breccia. Chemical sediments are soluble materials produced largely by chemical weathering that are precipitated by either inorganic or organic processes. Chemical sedimentary rocks often contain the products of biological processes such as shells or mineral crystals that form as water evaporates and minerals precipitate. The most abundant chemical sedimentary rock is limestone, composed chiefly of the mineral calcite. Rock gypsum and rock salt are chemical rocks that form as water evaporates and triggers the deposition of chemical precipitates. Organic sedimentary rocks are rocks that form from the remains of plants and animals. Examples are: coal, limestone, coquina Some of the features of sedimentary rocks that are often used in the interpretation of Earth history and past environments include stratification, or beds (the single most characteristic feature), bedding planes, fossils, ripple marks and mud cracks.