The Earth Sciences Museum is temporarily closed until further notice. We apologize to all of our visitors and groups for this inconvenience. Thank you for your understanding. Back to Rocks and Minerals Articles. 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 billion tons containing more than billion tons of iron. Iron ore is mined in about 50 countries. 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. A physician in successfully used iron to treat patients who were pale, lacking in energy and suffering from anaemia. Iron is among the oldest metals known to humans. Paleolithic Man used finely ground haematite as body paint.
Around BC, the Egyptians and Sumerians first used iron from meteorites to make beads, ornaments, weapons and tools. The time line of Iron Age varied geographically; for instance the Hittites forged iron they heated it, then hammered it, then cooled it quickly to produce iron that was harder than the bronze that people had been using before around the period of - BC and similarly according to Tewari , archaeological evidence indicates iron working in India occurred around to BC. By the time of the Roman Empire, iron was being used for beds, gates, chariots, nails, saws, axes, spears, fishhooks and tools for sharpening.
During the Middle Ages, with the introduction of the iron cannon and cannon ball, the consumption of iron increased to overtake copper and bronze as the most widely used metal. In the late 19th century the Age of Steel began, with wooden ships giving way to steel, machinery coming to factories and the invention of the railroad. Iron is indispensable to modern civilisation and people have been skilled in its use for more than 3, years. However, its use only became widespread in the 14th century, when smelting furnaces the forerunner of blast furnaces began to replace forges.
Iron ores are rocks from which metallic iron can be economically extracted. Most deposits of iron ore in the world are found in rocks known as banded iron formations BIFs. These are sedimentary rocks that have alternating layers of iron-rich minerals and a fine-grained silica rock called chert. Many of the banded iron formations that are being mined today were formed millions of years ago. About million years ago there was no or very little oxygen dissolved in the oceans.
However, the oceans did contain a lot of dissolved silica, which came from the weathering of rocks. Every now and again this silica precipitated out from the seawater as layers of silica jelly, which slowly hardened to become the rock we call chert.
Soluble iron oxide was also produced from the weathering of rocks and was also washed into the sea by rivers. About million years ago the oceans were inhabited by bacteria that developed the ability to photosynthesise and produce oxygen. There were seasonal 'blooms' that released huge amounts of oxygen into the seawater that reacted with the soluble iron oxide to form insoluble iron oxide.
This precipitated out of solution as the minerals magnetite and hematite forming layers of iron among the other layers of sediment on the sea floor. Over many millions of years these processes of precipitating silica and iron oxide were repeated over and over again resulting in the deposition of alternating layers of chert, hematite and magnetite.
The name banded iron formation comes from the characteristic colour banding of these huge deposits. The process continued for nearly a billion years and eventually let to the accumulation of oxygen in the atmosphere. Most of the world's important iron ore resources occur in banded iron formations, which are almost exclusively of Precambrian age i. BIFs occur on all continents. Mt Tom Price; iron oxides deposited along ancient, mainly Tertiary age river channels palaeochannels ; and iron oxide deposits formed from the erosion of existing orebodies detrital iron ore deposits.
The BIF enrichment deposits comprising hematite and hematite goethite are the most important in regard to resources and production. Yarrie , and the Yilgarn Block e. Koolyanobbing and in South Australia e. Extracting iron The blast furnace Iron is extracted from iron ore in a huge container called a blast furnace. Iron ore haematite. Iron III oxide. A compound that contains iron.
Burns in air to produce heat, and reacts to form carbon monoxide needed to reduce the iron oxide. Calcium carbonate.
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