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.

Not to be confused with crystallite size, which is referred to as "grain sizes" by metallurgists.
Granulometry
Basic concepts
Particle size · Grain size
Size distribution · Morphology
Methods and techniques
Mesh scale · Optical granulometry
Sieve analysis · Soil gradation
Related concepts
Granulation · Granular material
Mineral dust · Pattern recognition
Dynamic light scattering
Wentworth grain size chart from United States Geological Survey Open-File Report 2006-1195: Note size typos; 33.1mm is 38.1 & .545mm is .594
Beach cobbles at Nash Point, South Wales
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