Minecraft wiki entry for Block_and_item_duplication, associated text: Get an anvil and get either 9 iron ingot, 9 diamond, 9 coal, 9 gold ingot, 9 lapis lazuli, 9 redstone dust or 9 emerald. Rename 1 of the ores to something random, place it above the rest of the ores in your inventory and go to a crafting table. Craft a block of that ore and select 'craft all.' This will result in the player obtaining 1 block of (whatever ore you chose). The other 8 pieces will still be in your inventory.