My local feed store only sells a very small bag of crushed granite for ten bucks. I got a 20 lb bag of pea gravel from home depot and it has different sizes if small pebbles. I cant tell if they use much of it but do you think im in the right track? The crushed granite felt like it was about the same size as some of the gravel. The packaging of course was so I couldnt see the product to tell. Ten bucks seems like a rip off for a 1 lb bag! I have the gravel in a PVC feeder in the coop, and oyster shell in another one next to it.