What icon best represents magic?

[DustyPorViva]

For a gui, what do you think would best represent magic? For example, hearts represent health, shield represents defense... so on and so forth. But what can make the player see it and think "that must be my MP?"

This will be fairly large for an icon(32x32), and it is my belief that the icon should be full(aka no sticks or random sprinkles). Door suggested a star, and I like that idea... but at the same time I imagine a star seems childish or fairy-tale like instead of fitting for an RPG. There is also a crystal shard, but I dunno... seems too specific instead of general.

I already have the heart icon, so there is a style to adhere to... I don't think this matters for ideas, but if anyone needs to see it I will post it.