Since all four of these substances are natural, and alien in nature, it's hard to determine if they have been considered elements in fiction. I know Dilustel has never been stated as an element within DC continuity. Vibranium, as well.
@Dracade102: LOL I read the title of this thread the same way as Ron. I was expecting situations or "elements" of a comic story that wouldn't exist in real life and was amazed at how small the thread was.