The article focuses on elemental iodine chemical symbol I which has heaviest of naturally stable halogens and mentions that the source of iodine production are subsurface brines associated with oil and natural gas deposits. Topics discussed include how seaweed extracts and accumulates seawater on dry weight basis, 2016 world production of iodine estimated by the U.S. Geological Survey (USGS) and how supplier of iodine Sociedad Quimica y Minera de Chile S.A. (SQM) competed for market share.