Particle size

From DictionGloss

the diameter, in millimeters, of suspended sediment or bed material. Particle-size classifications are: [1] Clay—0.00024-0.004 millimeters (mm); [2] Silt—0.004-0.062 mm; [3] Sand—0.062-2.0 mm; and [4] Gravel—2.0-64.0 mm.