Can you solve the MAGNET RIDDLE? ft YouTube CEO Susan Wojcicki

6:42 you don't have to break it; you could hang both pieces of iron by the string and see which one align more easily with the north pole, that one is magnetized. You could also use the non magnetic yet metallic mallet and a multimeter (or a small led) and connect it to the mallet then move the each pieces of metal over the mallet really fast and see which generate current by the Faraday effect.