Silt is the middle of the three soil textural classes by size, its particle size range is from 0.05 mm to 0.002 mm.

"Silt" is composed of particles in siliciclastic sediment that range in size from 0.0039 millimeters (very fine silt) to 0.0625 millimeters (coarse silt), according to the Udden-Wentworth scale. In field geology, a mudrock has silt in it if it feels smooth to the fingers but feels gritty on the tongue. Silt and clay are collectively classified as mud.

Some of the information in this writeup was taken from the science dictionary at; I oversaw the development of the dictionary (the website was mothballed in 1998) and I believe I wrote the entry this is based on.

Silt (?), n. [OE. silte gravel, fr. silen to drain, E. sile; probably of Scand. origin; cf. Sw. sila, prob. akin to AS. seon to filter, sigan to fall, sink, cause to sink, G. seihen to strain, to filter, OHG. sihan, Icel.sia, Skr. sic to pour; cf. Gr. moisture. Cf. Sig, Sile.]

Mud or fine earth deposited from running or standing water.


© Webster 1913.

Silt, v. t. [imp. & p. p. Silted; p. pr. & vb. n. Silting.]

To choke, fill, or obstruct with silt or mud.


© Webster 1913.

Silt, v. i.

To flow through crevices; to percolate.


© Webster 1913.

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