Particle size:
In dealing with sediments and sedimentary rocks it is necessary that precise dimensions should be applied to such terms as CLAY, sand, pebble, etc. Numerous scales have been suggested, but in this work, the Wentworth-Udden scale is used, as it is widely accepted as an international standard. In the table which follows, particle size limits are shown, but within most groups further subdivision is possible; for example, sand may be described as very fine, medium, coarse, very coarse. Particle size is normally determined by hand measurement of pebbles, cobbles, and BOULDERS, sieving of GRAVEL, sand and silt and ELUTRIATION of silt and CLAY (7).
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