Mithril ore
Mithril ore is an ore, which can be smelted in a furnace with 4 pieces of Coal to create Mithril Bar with level 50 Smithing. Mithril can be mined from mithril rocks with level 55 Mining at Falador Mining Guild, but it's not recommended since it's too slow to be mined for good experience. You need pickaxe to be able to mine ores, which can be bought from Bob at the armory. Mithril Ore costs 162 coins from Bob.