The leading theory is that lodestones are magnetized by the strong magnetic fields surrounding lightning bolts. This is supported by the observation that they are mostly found near the surface of the Earth, rather than buried at great depth.

How was lodestone first magnetic?

Lodestone was well known to the ancients because it attracted iron. ... For centuries scientists have wondered how lodestone became magnetised. Dr Peter Wasilewski of Nasa's Goddard Space Flight Center suggested that it happens as a result of lightning strikes.

Are all lodestone magnetic?

Lodestone (also spelled loadstone) is a special type of the mineral magnetite. All varieties of magnetite display signs of magnetism, but of them, only lodestone possesses distinctly north-south polarity.