The lodestone, made from a piece of magnetite, which is naturally magnetic, was vital in the early centuries of navigation to ensure that the ship's compass worked properly. Until the mid-18th century, when improved compasses were developed, compass needles lost their magnetism quickly and had to be re-magnetised by stroking a lodestone along the needle's length.

Lodestones were often mounted in frames of brass, bronze or silver. This lodestone has a silver frame with a suspension ring, and is 'armed' with two pieces of steel at the bottom, which help to increase the magnetic strength of the lodestone.