Here is a set of six different sand grains I used in this thread:http://www.planetside.co.uk/forums/index.php/topic,22727.0.html
They don't have the correct size, because working in such small dimensions is a bit tricky.
(A tip for those who want to do exactly that [Thanks, Frank!!!]: In TG go to: Edit - Preferences - Input Settings - Custom Bindings - 3D Preview - Decrease near clip distance - and check, which button is assigned to this. Click into the 3d viewport and hit this button, and voilą no viewport clipping anymore.)
At the moments they have a diameter of four or five centimeters, so to get sand grains with real world dimensions you have to scale them down to 0.01 or 0.02.
Or use the grains as pebbles. But the subsurface scattering may be a bit too much. Or you can play with the shaders and try to use them as ice.