there are two broad classes of soils-coarse-grained soils and fine-grained soils.
Coarse-grained soils include gravel and sand,which consist of relatively large particles
visible to the naked eye;fine-grained soils,such as silt and clay,consist of much
smaller particles. The American Society for Testing and Materials (ASTM) Unified Soil
Classification System further divides gravels,sands,silts and clays into soil types
based on physical composition and characteristics.See table below