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
Granular material the partitions rather than spread evenly into both partitions as would happen in a conventional gas. This effect, known as the granular Maxwell's demon, does not violate any thermodynamics principles since energy is constantly being lost from the system in the process. Granular systems are known to exhibit jamming and undergo a jamming transition which is thought of as a thermodynamic phase transition to a jammed state. The Lubachevsky-Stillinger algorithm of jamming allows one to produce simulated jammed granular configurations. Excited granular matter is a rich pattern-forming system. Some of the pattern-forming behaviours seen in granular materials are: Some of