I checked out these little hematite pebbles (ground into rhomboid shapes) at a little gem and jewelry store at Sea-Tac airport when I came in on Thursday. Once you start playing with them, they are hard to put down (and so I had to buy a few!). The pebbles are magnetic, and immediately stick to each other if they get within a range of two inches or so. Electro-magnetism is one of the four forces between particles in our physical universe : electromagnetism, gravitational, weak nuclear and strong nuclear.