Smelted iron appears sporadically in the archeological record from the middle Bronze Age. Whilst terrestrial iron is naturally abundant, temperatures above are required to smelt it, placing it out of reach of commonly available technology until the end of the second millennium BC. In contrast, the components of bronze—tin with a melting point of and copper with a relatively moderate melting point of —were within the capabilities of Neolithic kilns, which date back to 6000 BC and were able to produce temperatures greater than .James E. McClellan III; Harold Dorn (2006). Science and Technology in World History: An Introduction . JHU Press. . p. 21. In addition to specially designed furnaces, ancient iron production required the development of complex procedures for the removal of impurities, the regulation of the admixture of carbon, and the invention of hot-working to achieve a useful balance of hardness and strength in steel.
