Ok, so I have this key to the Ebershard Mine... but I've cleared it completely and crawled it three times now - I can find no door that it opens. Any idea what I'm supposed to do with it?

~sbm

I believe it is used to unlock one of the interior doors that you opened in the mine.

All the doors were open for me already. :/

There's two metal gates opposite each other, it opens both of those. Behind one gate there's nothing and the other has goods stored as well as a chest.

Hmmm... that door was open because the Khajiit with the key comes running at you trying to kill you. I was wondering if the key just means I own the mine now or something?