Iron ore is the source of primary iron for the world's iron and steel industries. Because iron is the most widely used metal, iron ore is produced, traded, and consumed in large quantities in many countries. Annual world iron ore production usually exceeds 800 million long tons, of which about 90% is produced by 12 countries including the United States. U.S. production accounts for about 9% of world output. This Bureau of Mines report presents comprehensive data on iron ore including strategic considerations, problems, technology trends, reserves-resources, supply-demand relationships, economic factors and problems, operating factors and problems, and outlook to 2000.