Silt three grades fine, medium and coarse 0.002 mm to 0.006 mm to 0.020 mm to 0.063 mm). In actuality, silt is chemically distinct from clay, and unlike clay, grains of silt are approximately the same size in all dimensions; furthermore, their size ranges overlap. Clays are formed from thin plate-shaped particles held together by electrostatic forces, so present a cohesion. Pure silts are not cohesive. According to the U.S. Department of Agriculture Soil Texture Classification system, the sand–silt distinction is made at the 0.05 mm particle size. The USDA system has been adopted by the Food and Agriculture Organization (FAO).
Gravel Run (Black Creek) by acid mine drainage in the early 1900s. The acid mine drainage came from mines in and near the city of Hazleton. Gravel Run is entirely within the United States Geological Survey quadrangle of Hazleton. It drains a portion of the northwestern part of the city of Hazleton. It drains the older part of the city as well as the Green Ridge Territory. Gravel Run is one of eleven officially named streams in the watershed of Nescopeck Creek that has not been assessed by the Pennsylvania Fish and Boat Commission. Gravel Run was entered into the Geographic Names Information System