User blog comment:Unownshipper/Metallurgists Wanted: Rapture's Natural Resources/@comment-8299550-20140811221953/@comment-24819226-20140812064839

Well, as we found out in Burial at Sea Part 2 from an Audio Diary from Ryan himself, Raptrue uses aluminum for much of it's structure. http://bioshock.wikia.com/wiki/Building_the_Impossible! Guess that's one of the things where the novel isn't canon anymore. sm