http://mrhardy.wikispaces.com/Soil.swf
. Description of sand, silt, and clay classes. The Fine Earth Fraction
Size
Texture
Characteristics
Sand
2.0 mm -0.05 mm
gritty
Sand is visible to the naked eye, consists of particles with low surface area, and permits excessive drainage.
Silt
0.05 mm - 0.002 mm
buttery
Silt is not visible to the naked eye and increases the water holding capacity of soil.
Clay
< 0.002 mm
sticky
Clay has a high surface area, high water holding capacity, many small pores, and possesses charged surfaces to attract and hold nutrients.