Mossy Cobblestone is almost the same as normal Cobblestone, the only difference being that it is covered in moss. It is often used in combination with normal cobblestone to make buildings look old and like ruins. In Survival mode, it is currently only found in underground Dungeons, though it can be mined and used like normal Cobblestone. It will probably spread to other cobblestones in future versions making it act similar to grass. Another difference from normal Cobblestone is that Mossy Cobblestone will remain intact if TNT or a creeper explodes next to it.