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.
- 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
- 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
- Alumina for metallurgical purposes
- Chemical applications