Clastic Sedimentary Rocks: formed through consolidation of previously broken rock material, mostly composed of silicate minerals.
Shale. Mostly mud-sized particles (clay and silt), but shows parting of layers (fissility).
Mudstone. Mostly mud-sized particles, no preferred parting of layers (sometimes synonymized with shale). Siltstone. Silt-sized particles. Sandstone. Sand-sized particles.
Graywacke. Sandstone with an appreciable amount (>15%) of mud. Conglomerate. Sandstone containing abundant well-rounded particles of greater than 2-mm diameter.
Breccia. Sandstone containing abundant angular particles of greater than 2-mm diameter.
Chemical Sedimentary Rocks: formed through chemical precipitation of previously dissolved rock material, mostly composed of calcium carbonate, oxides, sulfates, and chlorides.
Limestone. Wide variety of rocks of different textures composed of CaCO3 (normally calcite but younger examples with aragonite). Dolomite. Composed primarily of mineral dolomite (Ca,Mg(CO3)2). Chert. Microcrystalline quartz precipitate with some H2O incorporated in the structure.
Hematite. Composed primarily of mineral hematite (Fe2O3), typically replaces reduced iron minerals.
Gypsum. Composed primarily of mineral gypsum (CaSO4 x 2H2O). Halite. Composed primarily of mineral halite (NaCl), also known as "rock salt." Coal. Composed of fossil plant material with sufficient organic carbon (as hydrocarbons) to be combustible.
Was this article helpful?