Silt

silt, predominantly quartz mineral particles that are between sand size and clay size, i.e., between 1-16 and 1-256 mm ( 1-406 – 1-6502 in.) in diameter. Silt, like clay and sand, is a product of the weathering and decomposition of preexisting rock. Hardened silt forms a sedimentary rock called

siltstone, which tends to deposit in thin layers sometimes referred to as flagstone because it is hard, durable, and flat, breaking into nearly rectangular slabs.

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silt

Sediment particles 0.00016–0.0024 in. (0.004–0.06 mm) in diameter, regardless of mineral type. Silt is easily transported by moving currents but settles in still water. An unconsolidated aggregate of silt particles is also called silt, whereas a consolidated aggregate is called siltstone. Silt deposits formed by wind are known as loess. Sediments are seldom composed entirely of silt but rather are a mixture of clay, silt, and sand. Clay-rich silt, upon consolidation, frequently develops parting along bedding surfaces and is then called shale. If parting does not develop, the massive rock is called mudstone.

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silt

a fine deposit of mud, clay, etc., esp one in a river or lake

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silt [silt]

(geology)

A rock fragment or a mineral or detrital particle in the soil having a diameter of 0.002-0.05 millimeter that is, smaller than fine sand and larger than coarse clay.

Sediment carried or deposited by water.

Soil containing at least 80% silt and less than 12% clay.

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silt, inorganic silt, rock flour

A granular material that is nonplastic or very slightly plastic and exhibits little or no strength when air-dried; usually has a grain size between 0.002 mm and 0.05 mm in diameter.

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Silt 

the fine-grained, soft sediment on the bottom of bodies of water, not altered by diagenesis. Between 30 and 50 percent of the particles it contains are less than 0.01 mm in size. Occurring in a fluid state under natural conditions, it assumes the properties of a solid body when dry. On the bottom of seas and continental bodies of water (lakes, rivers, and ponds) there are silts consisting of fine-grained products of rock decomposition (terrigenous, clayey, and lime silts) and silts made up of microscopic shells or the skeletal remains of marine organisms (globigerina, diatomaceous, radiolarian, pteropod silts). Silts that have been enriched by volcanic ash (volcanic mud) form a separate category. Sometimes silts are enriched with organic matter (sapro-pel) whose decay causes hydrogen sulfide contamination or putrefaction (“putrid silt”).

Some silts, including lake, pond, and lagoon silts, are used as fertilizer and for mineral feed supplements for livestock; they are also used in medicine, for pelotherapy.