Wentworth-Udden Particle Scale

A common system of grading the size of grains in a rock or sediment. If the grains can be seen the grade is at least silt, if it is not gritty between the teeth it is clay.

>256mmboulder
64 to 256mmcobble
4 to 64mmpebble
2 to 4mmgravel
1/16 to 2mmsand
1/256 to 1/16mmsilt
<1/256mmclay

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Subjects: Geology