which rocks are made formed when material sand, grit for clay
1.4 - Sedimentary Rocks. Sedimentary rocks are formed via the breakdown and redeposition of other materials, often older rocks. Sedimentary rocks are classified by their dominant particle size (sand, silt, or clay) and their mineral composition.lassic sedimentary rocks (i.e., sandstone or shale) are composed of minerals, grains and rock fragments derived from older rocks; while biogenic sedimentary rocks are made up of shells, their recrystallized remnants (i.e., limestone) or plant fragments (i.e., coal).