Just so you know, unobtanium is not the actual name of the mineral, it's a figure of speech. The figure of speech was kind of used incorrectly in the movie though, a better example would have been the element Tony Stark needed in Iron Man 2.
"In engineering, fiction, or thought experiments, unobtainium (also spelled unobtanium) is any extremely rare, costly, or physically impossible material, or (less commonly) device needed to fulfill a given design for a given application."