like we have seen a disk of aluminum spinning, and a permanent magnet repell the plate because apparently because of temporary hystersis and because the north or south field causes the same in the aluminum, so why wont a plate of ruby do the same thing? Are not all metals, crystals? Perhaps its just too big and difficult a question for you simple huumans,..eh?A synthetic ruby may be made of aluminum, but that is not ALL that it is made of. The primary material in all rubies is aluminum oxide. So you need oxygen. It\'s not like the stuff is hard to find... they probably don\'t even need to overtly add it when they manufacture rubies. And of course, that creates a world of difference. Ferric oxide (a.k.a. rust) isn\'t magnetic either, even though iron is very strongly so. Aluminum is NOT naturally magnetic (though I\'m sure it can be induced)... but if the parallel holds one might imagine that aluminum oxide would be just as nonmagnetic as ferric oxide, neh? As for metals being crystals... yes, that is so. But keep in mind also that just because all metals are crystals, it doesn\'t mean that all crystals are metals. Metals are (by definition) malleable, ductile, lustrous, and conductive. None of these things can be said of ALL crystals. Ruby may be a crystal, but it is not even vaguely a metal.Hey, magnets work on iron and steel, but not on non-ferrous metals.Other related question