The Reinforced Stone is a blast resistant block, good for building a Creeper/TNT safe bunker, or for protecting zones from a Nuclear Reactor. It can only be mined with a Iron Pickaxe or better, Mining Drill or a Diamond Drill and a Power Tool.
It is the third most blast resistant block after Bedrock and the End Portal Frame with a blast resistance of 150. (In Vanilla Minecraft, Obsidian has a blast resistance of 6,000; however, Obsidian resistance was decreased back by IndustrialCraft 2, lowering its blast resistance to 60). Reinforced Stone can withstand a Nuclear Reactor explosion when a wall of it is built 3 blocks thick. This way a bunker can be made that is completely able to withstand a Nuclear Reactor explosion. However, damage can still be dealt through the wall unless it is 5 blocks thick.