Like the crafting table, the smelting furnace is an essential item you'll struggle without in "Minecraft." When crafted and fueled, this device stays true to its name, smelting down metals, transforming sand into glass and cooking gathered food. Fuel comes in the form of several items, including charcoal or various wooden objects. Crafting the actual furnace only requires cobblestone.
The furnace is an essential item in "Minecraft," second only to the crafting table that lets you build it. For instance, it is impossible to craft tools made with anything better than wood unless you have a furnace to smelt down the ore. You also can't cook any of your food, which makes surviving difficult on "Easy" or higher difficulty. One minute ability you might also miss includes the ability to process a plant for dyeing another crafting object.
To build a smelting furnace, you need eight blocks of cobblestone. When you use a pickaxe to mine smooth stone, it breaks into one block of cobblestone. Right-click on your crafting table to open the 3-by-3 grid. Put a block of cobblestone around the grid's perimeter, leaving only the center square blank. This causes an icon of the furnace to appear beside the grid. Once you click and drag it to your inventory, the game creates the item and uses up the cobblestone; you can't undo it at this point. Place the furnace down as you would any other object. Right-click to open up the smelting screen.
It's not possible to smelt without fuel, but many in-game objects qualify for the task. The most readily available and weakest sources of fuel include tree saplings, sticks crafted from wooden planks or even the planks themselves. Only two objects in the game can light a furnace through an entire in-game night: a block of coal and a bucket of lava. Be wary of your bucket supply if you want to use lava, though; using lava as fuel destroys the bucket holding it when it's done.
Iron and gold ore are the two metals you can smelt down to ingot form. You can also smelt cobblestone to bring it back to its natural state while sand processes into glass. Tree trunks turn into charcoal while you can cook a cactus into cactus green dye, usable for crafting banners, green-stained clay or even cyan and lime dyes. Finally, you can cook gathered foods like raw fish, raw rabbit, raw beef and a potato to yield meals like cooked fish, cooked rabbit, cooked beef and a baked potato, respectively.