What Are Sedimentary Rocks? Sedimentary rocks are formed by the accumulation of sediments. There are three basic types of sedimentary rocks. Clastic sedimentary rocks such as breccia, conglomerate, sandstone, siltstone, and shale are formed from mechanical weathering debris.
There are three main classes of Rocks. They are classified according to how they originated. Igneous rocks form from cooling bodies of magma. Over time, various weathering processes erode these rocks and the resulting particles or chemicals settle into beds and are compressed and cemented into sedimentary rocks.