Lithium and Iridium are both metals that are found in the periodic table. Lithium is a soft, silvery-white METAL that is the lightest of all metals and is highly reactive. It is used in batteries, lubricants, and pharmaceuticals. Iridium is a hard, brittle, silver-white METAL that is the second densest element and is very corrosion-resistant. It is used in spark plugs, electrical contacts, and crucibles.