Hard to tell, but I bet its one of the three type of major rocks. I rule out Igneous due to the lack of (cant see it in the photo)small minerals that are usually associated with it. No veining or striations that are normal in Metamorphic ricks. My only bond head conclusion, some type of granite? It looks like they have been weathered pretty well. Judging by the chunks that are missing, its gray under there. I know, the nut case comes out
in me when it comes to rocks. I was a geology major for a few years then quit due to lack of jobs.
Also, depending on the area, I bet most rocks come from local area. I can't see them shipping a bunch of rocks across the country say, from AZ to up state NY?