Table T2.
Udden-Wentworth grain-size scale.
Particle type
Diameter
(mm)
Boulder
>256
Cobble
256–32
Pebble
32–4
Granule
4–2
Coarse sand
2–0.5
Medium sand
0.5-0.25
Fine sand
0.25–0.0625
Silt
0.0625–0.0039
Clay
<0.0039
