A lodestone is a piece of the mineral magnetite – a highly magnetized substance – that when suspended orientates itself with the direction and polarity of Earth’s magnetic field. Due to this innate ability, lodestones were used as the world’s first compasses, with their current name derived from the Middle English term for ‘leading stone’.
NASA scientist Dr Peter Wasilewski believes lodestones are created by the introduction of lightning discharges to magnetite. While short-lived a lightning bolt could create a very strong magnetic field capable of magnetising the mineral.