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Kathy Feick
The term “iron ore” is one which is used to describe those rocks sufficiently rich in iron to be used economically. Although elemental iron is ranked fourth in abundance in the Earths crust, metallic iron is virtually unknown on the surface of the Earth except as iron-nickel alloys from meteorites and very rare forms of deep mantle xenoliths. World resources of crude iron ore are estimated to exceed 800 billion tons containing more than 230 billion tons of iron.
Pure iron metal is silvery white, very ductile, strongly magnetic, and melts at 1528°C.
Major iron ore rocks:
- Massive hematite (most of the iron ore mined in the world comes from large deposits of massive hematite, most commonly in a banded iron formation)
- Pisolitic goethite/ limonite
- Banded metasedimentary ironstone
- Magnetite-rich metasomite
- To a much lesser degree rocks rick in siderite and charmosite
Uses:
- Iron accounts for approximately 95% of all metals used by modern industrial society
- Almost 98 % of iron ore is used in steel making
- Iron chloride and nitrite can be used as mordents and industrial reagents in the production of several types of inks
- Iron sulphate can be used as a fungicide
- Iron carbonyl can be used as a catalyser of many chemical reactions
- Jewellery
- Ornamentation
Mining:
Iron ore is mined in about 50 countries. The seven largest of these producing countries account for about three quarters of the world’s production.
Smelting:
Mined out of the ground, raw ore is a mixture of materials called ore proper and loose earth called gangue (waste). The ore proper is separated by crushing the raw ore are simply washing away the lighter soil. Breaking down the ore from its impurities is more difficult. This is achieved through a processed called smelting.
Smelting involves heating up the ore until the metal becomes spongy and the chemical compounds in the ore begin to break down. This process releases oxygen from the ore, one of the most common impurities in the metal. The facility used to smelt the iron is referred to as a bloomer. There, a blacksmith burns charcoal with iron ore and a good supply of oxygen. The carbon in the charcoal combines with the oxygen to create carbon dioxide and carbon monoxide. These gases are carried away, leaving behind the heavier elements. The metal never gets hot enough to melt completely, just hot enough to become a spongy mass containing iron and silicates. Heating and hammering this mass forces impurities out and mixes the glassy silicates into the iron metal to create wrought iron.
References:
Minerals, mines and quarries: http://www.minerals.dmitre.sa.gov.au/geological_survey_of_sa/commodities/iron_ore