Iron

Iron is one of the building blocks of industrial society. An element found beneath the Earth's surface, the extraction of this material scarred the land and killed many people who harvested it. Once above ground, the pliability and strength of ferrous metal allowed it to structure modern life, from skyscrapers to automobiles. The properties of iron have allowed its users to remelt and refashion it over and over, making it one of the most recycled materials in history.

Iron (Fe) ore is abundant across the planet, the fourth most common element in the Earth's crust. Artifacts containing iron (such as spear tips and beads) exist from human societies as early as the Paleolithic Age more than 30,000 years ago. Intensive mining and smelting (in which iron oxide is separated from the ore to form metallic iron) of iron to fashion tools and weapons developed throughout civilizations in China, India, and the Mediterranean between 1200 and 500 B.C.E. Biblical verses refer to the remelting and reshaping of old iron implements for agriculture and warfare, converting plowshares into swords (Joel 3:10) and swords into plowshares (Isaiah 2:4 and Micah 4:3). Iron and the alloys made with iron were vital to the rise of the Islamic world (including the development of the legendarily strong and flexible swords made of Damascus steel) and the guns and agricultural implements leading to the rise of nations in Europe.

English and colonial blacksmiths used old iron for horseshoes and other goods in the early modern period, getting the metals mostly from local sources. The American colonies produced iron from ore as early as 1645; by 1700, American iron accounted for almost 2 percent of world production and about 10 percent of British production. Due to restrictions from the mother country, the colonists could not establish new ironworks to produce finished products, limiting most of the colonial blacksmith's work to mending existing goods.

Iron was crucial to the fighting of the U.S. Civil War; the U.S. system of rifle manufacture (a precursor to modern mass production) depended upon the malleability and durability of iron. As the United States industrialized in the decades after the war, iron—and its harder, lighter alloy, steel—allowed cities to rise vertically, supplying the skeletons for skyscrapers. Iron formed the trains and the rails they rode on from coast to coast. Iron revolutionized naval and cargo ships. Demand for this ferrous metal spurred the digging of more mines, the opening of more foundries to turn iron into steel, and more scrapyards to reclaim disused metals.

Changing production techniques led to increased recycling of iron and steel. The Bessemer process, used widely in the late 19th century, used a limited amount of scrap iron, up to about 10 percent of the charge in order to regulate temperature. Open-hearth furnaces operated at higher temperatures than Bessemer converters, and they burned off phosphorus and impurities found in scrap that Bessemer converters could not remove, allowing for use of more scrap iron. The change was important because steel producers coveted ways to reuse old iron and steel, rather than mining virgin ore. Mining incurred great costs in capital and labor to extract ore from under the Earth's surface, and the hazards involved led to frequent injuries, deaths, and labor disputes. Environmental effects of mining range from the creation of sinkholes to the release of toxic chemicals into the groundwater, and mining remains one of the most dangerous occupations in industrial society.

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