Grain size Grain size Grain size (or particle size) is the diameter of individual grains of sediment, or the lithified particles in clastic rocks. The term may also be applied to other granular materials. This is different from the crystallite size, which refers to the size of a single crystal inside a particle or grain. A single grain can be composed of several crystals. Granular material can range from very small colloidal particles, through clay, silt, sand, gravel, and cobbles, to boulders. Size ranges define limits of classes that are given names in the Wentworth scale (or Udden–Wentworth scale) used in the
Gravel chub May and continuing into June. Adult gravel chubs have been spotted spawning by gathering on gravel bars in soft currents created by a rise in the waterline after hard rains. The gravel chub is considered a threatened species in many areas mostly due to the fact that it has a highly specific, clean habitat need. As of 1988 it was considered endangered in Kansas, under legal protection in Indiana and Wisconsin and considered a special concern in Kentucky, Minnesota and New York. Gravel chubs need constant mild currents with silt free riffles. Agriculture run-off is the biggest threat to this