Iron ore is the primary raw material used in the production of steel and, combined with steel, constitutes the world’s second largest commodity bloc by value, after crude oil. At least 800 million tonnes of iron ore are produced annually, whilst production of nished steel probably accounts for about 1.1 billion tonnes of production a year, emphasizing the scale of these closely-linked markets. Iron ore is categorized by dint of where it is produced and priced, and by its ferrous content, expressed as a percentage.