Cobble - Smaller than 300 mm and bigger than 80 mm.
Gravel -Smaller than 80 mm and bigger than 4.75 mm.
Gravels are further classified as
Coarse - For sizes between 80 mm to 20 mm. Fine -For sizes between 20 mm to 4.75 mm.
Sand -smaller than 4.75 mm and bigger than 75 micron
Sands are further classified as
Coarse -Size between 4.75 mm and 2 mm. Medium -Size between 2 mm and 425 micron. Fine - Size between 425 micron and 75 micron.
Silt - It has sizes less than 75 micron, It does not show or show little plastic behavior due to moisture and exhibits little or no strength when air dried.
Clay - It also of size less than 75 micron, but it can be identified by its behavior. It can exhibit plastic properties within certain range of moisture / water, and also exhibits considerable strength when air dried.
Organic matters - They are in various sizes and stages of decomposition.