Weathered particles of rocks, usually in silica, smaller than gravels and larger than silts, tipically about 0.06 mm to 5 mm. The particles are hard and will not crumble. Sand is used as an aggregate in mortars, plasters and renders as well as a component in concretes. The properties of sand used in a mix have major effect on its workability, final strengh and durability. (J. F. Gleeson).