What size defines silt particles?

• A. Less than 0.002 mm
• B. 0.002 to 0.05 mm
• C. 0.5 to 2 mm
• D. Greater than 2 mm

Answer: (B)

Sediment particle sizes are categorized by how big the grains are, with silt occupying a middle ground between clay and sand. Silt particles range from about 0.002 to 0.05 millimeters in diameter. That places them finer than sand (0.05 to 2 mm) but coarser than clay (less than 0.002 mm). This size range matters because silt can be carried in suspension by moving water and tends to settle as flow slows, forming fine sediments in rivers and floodplains. In soils, silt gives a relatively smooth texture and moderate water-holding capacity—more than sandy soils, but less than clayey soils. If the particles are smaller than 0.002 mm, you’re into clay; if they’re larger than 0.05 mm, you’re into sandy material.