IRON ORES

• ABOUT IRON

• THE EARTH'S CRUST

• HAEMATITE

• MAGNETITE

• IRON ORE RESERVES

• LOCATION OF THE IRON INDUSTRY

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ABOUT IRON

• Iron is the second most abundant metal, after aluminium, and the fourth most abundant element.
• Iron comprises 5% of the Earth's crust
• The principal ores used for the extraction of iron are haematite, Fe₂O₂, and magnetite, Fe₃O₄.
• These ores may contain between 20 and 70% iron by mass.
• The main impurities present in the ores are sand (silicon (IV) oxide, SiO₂) and aluminia (aluminium oxide, Al₂O₃).

THE EARTH'S CRUST

Indirect evidence suggests that the Earth's core consists mainly of an iron alloy. 

• The core has a radius of about 3470 kilometres (2150 miles).
• The radius of the Earth itself is about 6370km (3960 miles).
• The inner core of the earth is thought to be a solid with a radius of about 1200km. 
• Around this is a liquid outer core.  The turbulent flow of the liquid in this part of the core generates the magnetic field of the earth. 

The core is known to be predominantly iron although there is no consensus on its exact composition.  About 8 to 10% of the core probable consists of other elements such as nickel, sulphur (as iron sulphide), oxygen (as iron oxide) and silicon (as iron silicide).

HAEMATITE

Haematite is most often found in rocks once deposited by rivers or the sea.

The deep red colour of some rocks indicates that they contain haematite.  Most of these rocks were formed in parts of the tropics with wet and dry seasons.  During the wet season the minerals eroded from the land were washed to basins, deltas or coasts.  During the dry period the water evaporated and the sediments dried out, and iron compounds oxidised to iron oxide.  These rocks are often referred to as "red beds" and are usually fine-grained materials such as shales.

MAGNETITE

Iron is famous for its ability to act as a magnet, or to be attracted by magnets.  Native iron as well as iron alloys such as steel, and iron compounds such as some iron oxides (for example the ore magnetite) are also magnetic.  The property is created because each tiny crystal of iron can behave as a magnet, organising itself into the same direction as all those nearby.

The earliest knowledge of the magnetic properties of iron comes from the strongly magnetic rock known as lodestone or magnetite.  The word magnetite comes from the region called Magnesia in Greece, where loadstone was mined in ancient times.

A ball-shaped piece of lodestone has two regions where it will attract or repel other ball-shaped lodestones.  These places are known as the magnetic poles.

IRON ORE RESERVES

At least 12 countries in the world have proven reserves of over 10⁹ tonnes of iron ores.

These include:

• Australia
• Canada
• USA
• South Africa
• India
• Russia
• France

Each year of the order of 7000 million tonnes of steel are produced.  The major producers are Russia, the USA, and Japan- each of these producing well over 100 million tonnes annually.  Production in the UK is of the order of 20 million tonnes per annum.

World production of iron ore.

(Thousand metric tonnes unless otherwise specified)

LOCATION OF THE IRON INDUSTRY

• During the Industrial Revolution, new industries needed power supplies and raw materials such as coal or iron ore.  Industry located where these were easily available.  A pattern of industrial location developed where different areas specialised in industries using local resources.  For example South Wales developed a major coal industry, Sheffield was known for steel products (particularly cutlery) and Newcastle for ship building.

• Location near raw materials reduces transport costs, particularly of they are bulky or lose weight during the manufacturing process.

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