Bauxite

Bauxite

Bauxite is the principal aluminium ore

It is formed as a residual product over millions of years by chemical weathering of rocks containing aluminium silicates. It was first discovered in France in 1821, and has since been found in many locations around the world. Hydro has interests in two bauxite mines in Brazil.

  • Key features

    • Bauxite occurrences are widespread, mostly in tropical areas where there has been intense weathering to generate bauxite, however resources are tightly held by a few competitors
    • Bauxite usually occurs in a thin layer (typically 2 to 5 meters) near or at the surface
    • Worldwide production is about 250 million tonnes, and has been growing at an annual rate above 5% for the past decade, driven largely by Chinese demand growth
  • Application areas

    • Alumina for metallurgical purposes
    • Abrasives
    • Cement
    • Chemical applications
  • Product details

    • Bauxite is a mixture of minerals that contain various concentrations of hydrated aluminum oxides, as well as impurities. The primary ore minerals are gibbsite (alumina tri-hydrate), boehmite and diaspore (alumina monohydrates)
    • Gibbsite-rich bauxite is preferred as it can be refined at lower digestion temperatures than the other types of alumina bearing minerals
    • Bauxite is usually reddish-brown, but can also be white, tan, and yellow, depending on the type and concentration of iron minerals present. It also has a wide range of textures, but is typically dull to earthy in luster and can look like clay or soil

Bauxite in the value chain

Our value chain

The mineral bauxite is the starting point for production of aluminium metal

Aluminium is the third-most abundant element in the earth's crust. It is found in different types of minerals. Bauxite is the primary raw material for refining aluminium oxide, or alumina, which is used to produce primary aluminium metal. Bauxite deposits are mainly found in a wide belt around the Equator.

Alumina is refined bauxite and is a raw material for making aluminium

The raw material required for the production of primary aluminium is aluminium oxide, or alumina, a white powder refined from bauxite. To produce one tonne of aluminium in an electrolytic reduction process requires approximately two tonnes of alumina.

A large amount of electricity is needed to produce aluminium metal

The aluminium electrolytic process requires electric energy, about 13 kWh per kilo aluminium produced in modern production lines. Energy accounts for roughly a third of the cost of production of aluminium. Therefore, an important factor is long-term supplies of energy at affordable prices.

The production of primary aluminium takes place in large production lines

Pure aluminium is made from the alumina by a process carried out in electrolytic cells, where a carbon cathode placed in the bottom of the cells acts as an electrode. The anodes, also made of carbon, are consumed during the electrolytic process when the anode reacts with the oxygen in the alumina. Molten aluminium is tapped from the cells.

Other metals are added to the molten aluminium to form various foundry alloys

Molten aluminium is tapped from the pots and cast into logs, rolling slabs or ingots, depending on whether further processing is extruding, rolling or remelting. Small quantities of other metals can be added to the liquid aluminium to produce foundry alloys of different durability and tensile strengths.

Aluminium can be processed
in a cold and hot condition

Aluminium is ductile. Foil can be rolled to only 0.007 mm thickness, but will still be completely impermeable and lets neither light, aroma nor taste substances in or out. The metal itself forms a protective oxide coating and is highly corrosion resistant. Different types of surface treatment can further improve these properties.

Aluminium can be extruded and shaped into a variety of tubes and profiles

Aluminium ingot is heated and pressed through shaping tools, to make profiles for various products. Aluminium is increasingly taking over from copper as preferred metal for tubing in heat exchangers and air conditioners. There is no end to what shapes aluminium end products can take.

Only your imagination can limit the use of aluminium

Windows, car parts, doors, tubes, façade panels, cans… Hydro is the industry leader in many product areas for aluminium, especially in transport, buildings, packaging and lithographic plates. And in the end, the used product can be recycled – again and again.


Updated: October 3, 2016