Grain size

:This article deals with grain size in the context of geology, see crystallite for grain size in materials science.

Related Topics:
Geology - Crystallite - Materials science

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Grain size refers to the physical dimensions of particles of rock or other solid. This is different from the crystallite size, which is the size of a single crystal inside the solid (a grain can be made of several single crystals).

Related Topics:
Rock - Solid - Crystallite - Crystal

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Grain sizes can range from very small colloidal particles, through clay, silt, sand, and gravel, to boulders.

Related Topics:
Colloidal particles - Clay - Silt - Sand - Gravel - Boulder

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Size ranges define limits of classes that are given names in the Wentworth scale used in the United States. The Krumbein phi (φ) scale, a modification of the Wentworth scale created by W. C. Krumbein, is a logarithmic scale computed by the equation:

Related Topics:
United States - W. C. Krumbein - Logarithmic scale

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:phi=-log_2(hbox{grain size in mm}).

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In some schemes "gravel" is anything larger than sand (>2.0 mm), and includes "granule", "pebble", "cobble", and "boulder" in the above table. In this scheme, "pebble" covers the size range 4 to 64 mm (−2 to −6 φ).

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