Soil mechanics weathering of feldspar, which is the most common mineral present in igneous rock. The most common mineral constituent of silt and sand is quartz, also called silica, which has the chemical name silicon dioxide. The reason that feldspar is most common in rocks but silica is more prevalent in soils is that feldspar is much more soluble than silica. Silt, Sand, and Gravel are basically little pieces of broken rocks. According to the Unified Soil Classification System, silt particle sizes are in the range of 0.002 mm to 0.075 mm and sand particles have sizes in the range of 0.075
Silt out which is also likely to disturb silt where it makes contact, and the underwater work may also disturb silt. For these reasons surface supplied divers must often operate in very poor visibility. Remotely operated underwater vehicles and submersibles manoeuver by using thrusters, and the water blast from thrusters has a similar effect to the wash from fins. Silt outs are dangerous situations for scuba divers, particularly in enclosed spaces or when there is no direct access to the surface (an overhead environment). Training courses in overhead environment diving, such as wreck or cave diving teaches various methods to cope with