Bauxite

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Bauxite is a reddish-brown rock that holds the world’s main supply of aluminum and gallium. It’s made mostly of aluminum minerals called gibbsite, boehmite, and diaspore, mixed with iron oxides, clay, and small amounts of other minerals. It looks dull and varies in color from reddish-brown to white or tan.

The rock got its name from the village Les Baux in Provence, France, where it was first found in 1821 by Pierre Berthier. There are different ways scientists classify bauxite, but the big idea is that some bauxites form in tropical soils (lateritic) and some form in karstic, or carbonate, systems.

Guinea is the largest producer, followed by Australia and China. Bauxite is usually strip mined because it lies near the surface with little overburden. Recycling aluminum saves energy and can help stretch world bauxite reserves.

How it becomes aluminum
- Most bauxite is turned into alumina (aluminium oxide) through the Bayer process. Bauxite is heated with a strong sodium hydroxide solution under pressure, which dissolves the aluminum compounds.
- The undissolved waste (red mud) contains iron oxides, silica, and other minerals.
- After filtering, alumina is produced by precipitating gibbsite and then heating (calcination) to convert it to alumina.
- The alumina is dissolved in molten cryolite and then aluminum is produced by electrolysis in the Hall–Héroult process.

Bauxite also naturally contains gallium, which can be extracted from the processing liquor, though only a portion of available gallium is recoverable. The ore can also be a source of vanadium.

Environmental and social impacts
- The Bayer process creates a highly alkaline byproduct called red mud, with a high pH, which can contaminate soil and water if not managed properly.
- Red mud can dry into dust and cause health problems; spills have harmed ecosystems in places like Hungary.
- Mining often clears land, disrupts habitats, and can affect water and soil quality. In some regions, bauxite projects have sparked protests and conflicts with local communities and Indigenous peoples.

Other notes
- Bauxite can liquefy if it gets very moist during shipping, which can make ships unstable. A simple can test can help indicate the risk.
- In recent decades, increasing aluminum recycling helps cut the need for new bauxite and saves energy.

In short, bauxite is the key ore for aluminum, processed through the Bayer and Hall–Héroult methods to produce metal, while its extraction and processing pose environmental and social challenges that communities and industries continue to address.