Needles were magnetized by stroking them with a lodestone, a lump of magnetic rock called magnetite.
There is no need to dwell upon the early crude theories of the action of amber and lodestone.
Steel magnets of great strength and of any convenient form may be prepared either in this manner or by treatment with an electromagnet; hence the natural magnet, or lodestone as it is commonly called, is no longer of any interest except as a scientific curiosity.
With the constant practice of this operation it is hardly possible that the repulsion acting between like poles should have entirely escaped recognition; but though it appears to have been noticed that the lodestone sometimes repelled iron instead of attracting it, no clear statement of the fundamental law that unlike poles attract while like poles repel was recorded before the publication in 1581 of the New Attractive by Robert Norman, a pioneer in accurate magnetic work.
Cardinal Jacques de Vitry, bishop of Acon in Palestine, in his History (cap. 89), written about the year 1218, speaks of the magnetic needle as "most necessary for such as sail the sea"; 1 and another French crusader, his contemporary, Vincent de Beauvais, states that the adamant (lodestone) is found in Arabia, and mentions a method of using a needle magnetized by it which is similar to that described by Kibdjaki.