Soil mechanics necessary to run water through the sieves to wash the coarse particles and clods through. A variety of sieve sizes are available. The boundary between sand and silt is arbitrary. According to the Unified Soil Classification System, a #4 sieve (4 openings per inch) having 4.75mm opening size separates sand from gravel and a #200 sieve with an 0.075 mm opening separates sand from silt and clay. According to the British standard, 0.063 mm is the boundary between sand and silt, and 2 mm is the boundary between sand and gravel. The classification of fine-grained soils, i.e., soils that are
Polish Soil Classification effect of specific groups of soil forming processes. Soil types are divided into subtypes. Geological origin of bedrock described by "rodzaj gleby" describes geological origin and properties of material from which the soil was formed. It is not the same as soil family from USDA Soil Taxonomy. Examples can be: granitoid, basalt, amphibolite, sandstone, limestone (with specified period of formation), gypsum, glacial till, sandur sand, loess and others. Sizes of soil particles and texture of soil material are very similar to USDA classification. It makes possible correlating results of particle size analysis of soils described using USDA and Polish Soil