Mudstone is a fine-grained sedimentary rock primarily composed of clay and silt particles. It forms from the compaction of mud, which can include a mixture of minerals, organic matter, and water. Mudstone is typically gray, brown, or greenish in color and is known for its ability to retain moisture. This rock type is often found in river deltas, lake beds, and ocean floors, where sediment accumulates over time. Mudstone can serve as a source rock for hydrocarbons and is important in the study of geology and paleontology, as it can preserve fossils and other geological features.