Stream sediment is a type of sediment that is composed of particles that have been transported by a stream or river. It is usually composed of SILT, which is a type of soil that is made up of very small particles. SILT is typically between 0.004 and 0.06 millimeters in diameter and is composed of clay, quartz, and other minerals. Stream sediment is an important part of the hydrological cycle, as it helps to replenish soils and provide nutrients for plants.