When you put gold into a furnace, it won't smelt. Iron and other materials will smelt but for some reason gold will not. This has either been already mentioned somewhere (could not see it when searched for) or it is an intentional part of the game (why you still get gold ore doesn't make sense though). Hopefully this bug gets fixed because I want  to go to the nether but have over  stack and a half of unsmelted gold ore in my chest.