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 dogfish 450 m depth. Granular dogfish The granular dogfish, "Centroscyllium granulatum", is a little-known, very small dogfish shark of the family Etmopteridae, endemic to the Falkland Islands. The granular dogfish has no anal fin, two dorsal spines with the second one much larger than the first, a large second dorsal fin, a long abdomen, small pectoral and pelvic fins, a large eye, prominent nostrils and spiracles, and brownish-black coloration. It is very small, growing to only 28 cm. They have only been found around the Falkland Islands in the South Atlantic. Almost nothing is known about this shark. It has been