Originally Posted by Lord
Was it actually shown that the staff took powers from the Tesseract or only speculated by a human character, in that case it could actually be a stone
It was stated specifically by Nick Fury in the movie to be Tesseract-powered, and Kevin Feige specifically confirmed this in several interviews.
Yeah, SHIELD probably has it in their possession; and no, it isn't likely to have powers any more, now that it's separated from the Tesseract. It's probably being kept in a great big crate in some nameless warehouse somewhere, being watched over by top men.