Sand usually contains abundant silica, but it generally is not pure silica.
Properties of River SandTextural composition(% by weight)Coarse Sand (4.75 - 2.00 mm)6.6Medium Coarse sand (2.00 - 0.425 mm)73.6Fine sand (0.425 - 0.075 mm)19.8
From the yellow sand in the river.
The river runs however long, all the while picking up sediment, sand, rocks, etc. and continue doing this for the river's length, and at the very end of the river (mouth), all of this sediment is deposited, leaivng sand at the river mouth.
Maximum value of dry density of river sand is 1.7 gm/cc
plaster sand
You pick it up.
Sand Bar
A lot of dirt, sand and rocks from where the erosion was sunk into the sand.
sand bars
ridge of sand built up by currents in a river or coastal waters
The abrasion and attrition combined with hydraulic action on the river bed and the river banks erode away the underlying rock which results in small grains of rock we call sand. Depending on the speed of the river and the size of the particles, the sand will be deposited by the river at different stages (usually though it is found near the mouth of the river).
sand dunes i think?