Lodestones are naturally magnetized pieces of the mineral magnetite. They are naturally occurring magnets, which can attract iron. The property of magnetism was first discovered in antiquity through lodestones. Pieces of lodestone, suspended so they could turn, were the first magnetic compasses, and their importance to early navigation is indicated by the name lodestone, which in Middle English means "course stone" or "leading stone", from the now-obsolete meaning of lode as "journey, way".
Lodestone is one of only a very few minerals that is found naturally magnetized. Magnetite is black or brownish-black with a black streak, with a metallic luster and a Mohs hardness of 5.5–6.5.