An article by Alan Millard in the Bible Review talks about how iron was used anciently to decorate royal beds, thrones, bracelets and other jewelry. The article explains how iron was “highly prized” just like other precious metals and was considered a treasure.
I am fairly confident that if I tried to give my wife an elegant pair of iron ear rings, she would not hold them in as high regard as gold or even silver ones. I am also confident that Joseph Smith would not have considered iron a precious metal. He would not have included iron in the same class as gold, silver and copper if he were writing the Book of Mormon based on his own experiences.