[thedoc (OP)]

Scott asked the Naked Scientists:
   Why do grains of sand seem to be one size in dunes and on beaches?
What do you think?

[JimBob]

These sands are all one chemical compound and thus, crystal structure.

[RD]

The grains are of similar size as they have been sorted by the action of water and/or wind ... https://www.nps.gov/grsa/learn/education/classrooms/all-sand-grains-great-and-small.htm


https://commons.wikimedia.org/wiki/File:Sand_from_Gobi_Desert.jpg

[evan_au]

Why do grains of sand seem to be one size in dunes and on beaches?

1.Possibly because we can't see them easily with the naked eye, so we don't check their sizes too carefully.

2. Sand grains are sorted by wind and running water. Very small particles tend to be carried much farther than heavier particles. So the sand you see in one location is in that location because of its size.

Oops - crossover with RD...

[JimBob]

Yes, I ignored sorting. BUT the smaller the size-es are also governed by crystal structure