Aluminium is the most abundant metal in the Earth's crust, yet almost none of it is found as metal. It is locked inside clays and silicates that are expensive to break apart. Bauxite is the exception: a rock in which nature has already done much of the work, concentrating aluminium into hydroxide minerals that industry can extract economically.
The name comes from Les Baux-de-Provence in southern France, where the French geologist Pierre Berthier identified the ore in 1821. Two centuries later, bauxite remains the starting point for nearly all primary aluminium made anywhere in the world.
What bauxite is made of
Bauxite is not a single mineral. It is a rock made of several, and the mix decides how it can be used.
- Gibbsite, Al(OH)₃, the aluminium hydroxide most common in tropical bauxites, including those of India's west coast.
- Boehmite and diaspore, two forms of AlO(OH), more common in older or more deeply buried deposits.
- Iron oxides such as goethite and hematite, which give bauxite its red, brown or ochre colour.
- Kaolinite and other clays, the main source of the silica that buyers watch closely.
- Titanium dioxide, usually as anatase, and small amounts of other trace elements.
On a lab report these minerals are expressed as oxides: Al₂O₃ (alumina), SiO₂ (silica), Fe₂O₃ (iron), TiO₂ (titania) and LOI, the loss on ignition, which is mostly the chemically bound water driven off when the ore is heated. If you are new to these reports, our guide on how to read a bauxite specification sheet walks through each line.
Where bauxite comes from
Most of the world's bauxite is lateritic: it formed where hot, wet tropical climates weathered aluminium-bearing rocks for millions of years. Rain leached away the soluble elements such as silica, calcium, sodium and magnesium, and left behind a residue enriched in aluminium and iron. A smaller share is karst bauxite, formed on limestone and dolomite, typical of parts of southern Europe and the Caribbean.
India's deposits are overwhelmingly lateritic. On the Konkan coast of Maharashtra, bauxite caps the weathered Deccan basalt, which is the setting of Minequor's 175-acre mine in Raigad. We look at that process in detail in how lateritic bauxite forms on the Deccan basalt.
What bauxite is used for
Around nine-tenths of the world's bauxite goes to alumina refineries, but the remainder supports several industries that need a high-alumina raw material.
| Use | What the buyer needs | Typical product |
|---|---|---|
| Alumina refining | High available alumina, low reactive silica | Smelter-grade alumina, then aluminium |
| Refractories | Very high alumina after calcining, low iron and titania | Bricks, castables, kiln linings |
| Abrasives | High-alumina, low-impurity feed for fusion | Brown fused alumina grits |
| Cement | An alumina corrective with a predictable iron and silica profile | Clinker raw mix, calcium aluminate cement |
Each of these uses corresponds to a commercial grade. Minequor supplies metallurgical, refractory and abrasive and cement grades from the same ore body, separated by grading and lab testing.
Why the details matter
Two bauxites with the same headline alumina can behave very differently in a refinery or a kiln. The form the alumina takes, how much of the silica is reactive, and how consistent the chemistry is from lot to lot all change the economics for the buyer. That is why serious bauxite trade runs on specifications, sampling and certificates rather than on a single number.
The short version
Bauxite is a weathered rock rich in aluminium hydroxides, mixed with iron oxides, clays and titania. It feeds the aluminium industry first, and refractories, abrasives and cement after that. Its value depends less on how much alumina it contains than on what form that alumina takes and what comes with it.