Barium

Barium is a soft, silvery alkaline earth metal that reacts readily with air and water. It is too reactive to occur naturally as a free metal; instead, it is found in compounds, chiefly the mineral barite, or barium sulfate. Industry mines barite and processes it into other barium compounds. To obtain the metal, producers use aluminum to remove oxygen from barium oxide. Barium compounds give some fireworks their green color. Another compound has a surprising medical role: specially purified barium sulfate helps the digestive tract show up in X-ray images. Unlike poisonous water-soluble barium compounds, barium sulfate is almost insoluble, so very little is absorbed by the body.