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sand




A collection of mineral particles, with diameters in the range 0.125–2 mm, worn away from rock by erosion. It can be graded according to particle size: fine (0.125–0.25 mm); medium (0.25–0.5 mm); coarse (0.5–1.0 mm); and very coarse (1–2 mm). Sands result from erosion by glaciers, winds, or ocean or other moving water. Their chief constituents are usually quartz and feldspar. Black sand (containing volcanic rock) and coral sand can also occur. See also sandstone.


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   • GEOLOGY AND PLANETARY SCIENCE