An upheat pickaxe is used to mine bars from metal rocks. It, however, needs 65 Attack to wield and 90 Mining to mine with. Also it increases the players chances of obtaining an uncut oceanstone or an uncut thunderstone while mining. Mining bars only occurs when you have other ores needed for your bar with you and have enough high smithing level. It is basically a wieldable Superheat Item spell. If clay or coal is mined, it will result in standard mining.