Sedimentary Rocks

Rocks formed at or near the Earth's surface by the accumulation, compaction and cementation of mineral or organic particles, or by direct chemical precipitation from water, following the clastic, chemical, biochemical and organic divisions of standard sedimentary petrology. Includes clastic rocks built from broken rock and mineral fragments of varying grain size (conglomerate, breccia, sandstone, greywacke, siltstone, mudstone, claystone, shale), chemical and biochemical rocks precipitated from solution or built from organic remains (limestone, chalk, dolomite, travertine, chert, flint, evaporite, ironstone), an organic rock formed from compressed and heated ancient plant matter (coal), and a mixed clay-carbonate rock that lithifies from both a clastic and a chemical component (marl). Belongs here: any material that formed at the surface from the deposition of particles or the precipitation of dissolved minerals, never from melting. Does not belong here: material that cooled from magma or lava (Igneous Rocks), or a sedimentary rock later transformed by heat and pressure into a new rock, such as shale into slate or limestone into marble (Metamorphic Rocks).