I thought I remembered reading somewhere that you can mine for rocks using the sledgehammer. I went to the Quary, held the sledgehammer over one of the rocks and the option to "Mine" popped up, indicating if I held the left mouse button, I could mine. When I do that, I get the circle with the white bar spinning, like you see just before you start an action (loading a magazine, opening a can etc) but I can't mine. If I need a pickaxe, why would the sledgehammer give me the "Mine" option?!