The other day I was on Terra Genesis and someone asked if there was an easy way to grade sand. I recalled the solution I came up with back when i first started collecting cheap terrain materials. You don't really need any specialist equipment, other than what you may have in your hobby arsenal - I got a small plastic bottle, similar to the kind you get chewing gum in, I cut a hole in the circular lid and filled it with sand. Then I sandwiched two layers of granny grating inside the lid.
The grating was rotated so that the hole from one is partially obstructed by the next layer. By twisting the layers you can change the gauge of the apperture from fine sand to big particles. Then shake out into a box.
I keep one box with the chunky pieces then pinch and scatter those on my bases so they are 75% covered, then I bury the remaining 25% in whatever I can get. As you can see in the pictures it's missing the second layer but you should be able to see How it's made.
I'm sure any other brand of chewing gum bottle would make do.
Here's an example of how the sand is graded. Clearly the basing helps pick out the variety but it's there in spades!
And more recently:
Anyway, just thought I'd share a quick tip.