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
Fern House Gravel Pit Fern House Gravel Pit Fern House Gravel Pit is a 1.3 hectare geological Site of Special Scientific Interest in Fern, near Bourne End in Buckinghamshire. It is also a Geological Conservation Review site. This site exposes the Pleistocene Taplow Gravel formation, and may help to elucidate a poorly understood period in the history of the River Thames, between glacial Anglian stage, around 450,000 years ago, when the river was diverted south to its present course, and the warm Ipswichian around 120,000 years ago. Fossils found at the site include straight-tusked elephants and mammoths. The site is on private land with