Sure can, and as long as you get a variety of stone sizes the birds will pick out what they need. Someone already mentioned granite and that is great just resist the idea of heading down to the local granite countertop fabrication shop. That can be some pretty exotic stone and all those pretty colors are usually some form of toxic heavy metal.
It is not unusual to find granite quarries competing for the same land or right next to a uranium mine. In the last few years here in Oklahoma the DEQ has forced the shops to landfill their sand and sludge instead of dumping it or letting it go into the drains.
Most of the granite found in the U.S., even in high radiation background areas like CO are going to be just fine for chickens. I wouldn't be breaking up rocks though, grab it from a stream so it has the jagged corners worked off. BTW, it makes an excellent soil amendment too.
