So pebbles on the beach are smooth, but why isn't sand?

Question

Grains of sand are not smooth at all!

Please don't bother answering different questions like why pebbles are smooth, or saying the same as 3 other people.
I do not believe that most sand is smooth when looked at close up.
I used to be tolde that sand comes from pebbles that hav been made smaller and smaller by erosion. I don't think this is true since sand does not look like small smooth pebbles. Looks to me as if sand must (have been) created by a different process.
Where are these crystaline rocks being crunched up into sand?

Ok, I've taken independent advice. I accept that some sand is smoother than others and that wave action on beaches will smooth the sand grains. So beaches near cliff will likely have sharper (newer) sand.
Byt that does not explain how the sand grains in the sandstone rock was formed with sharp grains. What formed all the sharp grains that formed the sedimentary rock, and why didn't they get smoothed out.
I guess they must have formed very quickly?

Greebo are you daft or what?
I know why pebbles are smooth which is why I explicitly did not ask that.
READ THE QUESTION

Answer 1

If you throw a rock at another rock you whould expect a mark, damage, one of the rocks to break. If you threw a grain of sand, what then? The grain of sand, doesn't throw very well, relatively high surface area, it resists the destructive force of the throw.

throw an insect at a wall, same effect, but if you were to scale an insect up to human size it would crush its self.

I agree with some points made by others, but this seems to be over looked.

Answer 2

It has to do with the volume of each. A big pebble, with a sharp point, it easy to knock off. In a small sand grain, a corner may be a significant portion of the volume of the object, so knocking it off to round is harder. Basically, if you knock off a sharp corner, you just create another sharp corner usually. It takes a delicate or percise action to smooth a small grain.

Also, most beach sand is really smooth when you look at it microscopically. It just feels rough because it's small, but the roughness you feel is the whole grain pushing down at once.

The mineral form and cleavage can also make sharpness (e.g. Feldspar), but 99% of beach sand is quartz which has no cleavage.

Answer 3

sand is made of crystals, but pebbles are rocks
crystals form by molecules of a mineral attaching themselves to each other
rocks are compressed mud

Edit:
To respond to the additional details

some sand feels smoother than others:
yeah, the grains in the smooth sand are smaller so you cant feel any sharp points, but the grains are the same shape.
experiment:
go to any diy shop and feel diffrent grades of sand paper (the higher the number on the paper, the smaller the grain size)
high numbered paper feels smoother

not all beaches are smooth sand:
yup that is purely to do with tides and "long shore drift" its a process similar to winnowing flour, the tides will either concentrate or remove fine grained.
experiment: from a builders shop get some coarse and some fine sand, mix the 2, on a breezy day pour the mixture onto the ground from the same height as your head.
the small grains will be blown to one side, the large ones (that feel rough) will not drift so far.

pebbles (rocks) are mud, sand is crystals:

crystals grow very slowly one molecule at a time will attach itself to an existing crystal in a set pattern (defined by the atomic properties of the molecule). the set pattern, when repeated many times will develop into a geometric shape with flat sides and sharp corners.
If you break a crystal, it is likely to shear (split) along a plane parallel to one of the sides forming smaller crystals with flat sides and sharp corners (sure it is possible to smooth out the corners by polising with something harder like diamond, but that takes dedicated, accurate work)

rocks are squashed mud:
mud contians mineral crystals and biological matter (its dirt), bury it and heat it (maybe even melt it) to form "amorphous lumps", that is hard solids that do not have an overall crystal structure. whan a rock breaks it will break along random planes, easily breaking off sharp corners

Answer 4

Depending on where you are at sand can be smooth, course, large or small. Some beaches in the Caribbean have sand that is like powder and others like in Hawaii have black sand beaches that the sand is like small stones. But most larger pebbles that are smooth are sort of like river rocks that are continuously rolled over other rocks and sand to smooth them out.

Answer 5

thats becuase the pebbles are larger so the waves just smooth um out, the grains of sand are rocks that have been pounded on by the ocean for years so they're broken up into smaller forms.

Answer 6

In Hawaii the sand is black from the broken down lava rock and the stones that are smooth are too hard for the water to break down so they become smooth like in rivers.

Answer 7

Pebbles get erroed away, making them smooth. Sand are grains of rock. If the sand was larger (More surface area ) then you woudl also notice sand is smooth too

Answer 8

The pebbles are smooth because the sand grinds them smooth but you already know this so why did you ask this question?

Answer 9

A tao has it right, sand is composed of individual crystals of minerals, quartz, feldspar, biotite. The form of these grains is dictated by the crystalline structure, not by erosive wave action, which tends have sharp angles

Answer 10

Its the mixture of sand and water that makes the pebbles smooth. I think. Don't quote me on that.