These are the kinds of questions addressed in What Things Are Made Of.
Quote from the book:
Contrast media in medical diagnostic imaging contain as much as 60% iodine, familiar as a disinfectant. Chile’s northern deserts harbor nitrate-rich deposits that also rank as the world’s largest supplies of iodine, even though only about 0.05% of the ore is calcium iodate, Ca(IO3)2.
Fact: In 2005, the U.S. imported 72% of the iodine it consumed.
Quiz: Which of the following do you think the U.S. is self-sufficient in (that is, the U.S. is a net exporter)? Gold, bauxite (aluminum ore), nickel, tungsten. Answer next time!