Sounds sorta like the world I was working on. A moon loaded with a make-believe ore was mined out by an advanced alien race. The moon shattered and the shards fell into the upper atmosphere of the gas giant it orbited. The ore was energized by the descent somehow and defied gravity, causing the shards to hover and become stable.

Life blooms and evolves eventually and you have a campaign setting in a vast airy wilderness. =) Someday I'll finish writing that one up.