Silt is made from mineral and rock particles that are smaller than sand. Some particles of silt are so tiny that they are very hard to see with the naked eye. Particles in silt are less than 0.002 inches across, and silt is found in soil and deposited and transported by wind, ice and water.
Silt is created by erosion, or the wearing away of rock. Generally, water flowing over rock slowly chips away particles that float away as silt. To be classified as silt soil, soil must be 80 percent silt. Silty soil is slippery when it gets wet, and when deposits of silt become compressed, siltstone rocks form.