Rock

Bauxite

A weathered residual rock rich in aluminium hydroxides — the world's only significant aluminium ore.

Bauxite is not a mineral but a rock — a mixture of aluminium hydroxide minerals with iron oxides and clay, formed where intense tropical weathering has leached almost everything else away. Its red colour comes from the iron left behind alongside the aluminium.

It is worth being precise about what bauxite is, because it is routinely described as 'aluminium ore' in a way that implies a mineral. It is a weathering product, and its variable composition is why refining it takes a chemical process rather than simple smelting.

How it forms

Formed by prolonged chemical weathering in hot, wet climates with good drainage, where silica and other soluble components are washed out over millions of years and aluminium and iron oxides remain. Most bauxite deposits are consequently tropical or were tropical when they formed.

Medium confidence Weak evidence

How we know: checked recently · only one source, so there is nothing to cross-check it against · stated directly by the source.

How this connects

Where a connection has been confirmed by an outside reference, that reference is named beside it.

is an ore of

Aluminium — element · via alumina — bauxite is refined by the Bayer process before smelting

is a source for

Aluminium oxide — compound · dissolved out with hot caustic soda in the Bayer process
Gallium — element · as a by-product of the Bayer process

is used as

Alloying — application · the ore that supplies essentially all primary aluminium

is an input to

Bayer process — process · the ore, dissolved selectively so the iron and silica are left behind

contains

Iron — element · the iron oxides left behind when the aluminium hydroxides are dissolved out, and the reason bauxite is red

is sourced from

Basalt — rock · the residue of prolonged tropical weathering, which strips the silica and alkalis out of an aluminosilicate rock and leaves the aluminium behind — basalt is one common parent among several

is used in

Mining and quarrying — industry · the only aluminium ore worked at scale

is a component of

Refractory brick — material · calcined, as the alumina source for the high-alumina grades

Sources

Material World
Our own writing

Questions this page answers

Where it comes from, and what it becomes

Follow Bauxite back to what it starts as, and forward into what it becomes. Each step is a documented one — a real route material takes, not a chain of inference.

Upstream — what it comes from

Bauxite → is sourced from (the residue of prolonged tropical weathering, which strips the silica and alkalis out of an aluminosilicate rock and leaves the aluminium behind — basalt is one common parent among several) → Basalt → is sourced from (partial melting of mantle peridotite is what basalt magma is — the residue left behind stays peridotite, depleted of what went into the melt) → Peridotite → is composed of (the mineral that defines the rock and gives it its name — a peridotite is olivine-dominant by definition) → Olivine
Bauxite → is sourced from (the residue of prolonged tropical weathering, which strips the silica and alkalis out of an aluminosilicate rock and leaves the aluminium behind — basalt is one common parent among several) → Basalt → is composed of (an early-crystallising constituent of basaltic magma) → Olivine
Bauxite → is sourced from (the residue of prolonged tropical weathering, which strips the silica and alkalis out of an aluminosilicate rock and leaves the aluminium behind — basalt is one common parent among several) → Basalt → is composed of (calcium-rich plagioclase is a defining constituent of basalt) → Plagioclase
Bauxite → is sourced from (the residue of prolonged tropical weathering, which strips the silica and alkalis out of an aluminosilicate rock and leaves the aluminium behind — basalt is one common parent among several) → Basalt → is composed of (carried up as xenocrysts in alkali basalt and recovered from the gravels the basalt weathers into, rather than mined from the rock itself) → Sapphire
Bauxite → is sourced from (the residue of prolonged tropical weathering, which strips the silica and alkalis out of an aluminosilicate rock and leaves the aluminium behind — basalt is one common parent among several) → Basalt → is composed of (lining vugs and geodes in weathered basalt flows, which is where nearly all of the world's amethyst comes from — the cavity is a gas bubble the lava left behind) → Amethyst
Bauxite → is sourced from (the residue of prolonged tropical weathering, which strips the silica and alkalis out of an aluminosilicate rock and leaves the aluminium behind — basalt is one common parent among several) → Basalt → is sourced from (partial melting of mantle peridotite is what basalt magma is — the residue left behind stays peridotite, depleted of what went into the melt) → Peridotite → is composed of (the magnesian end of the olivine series, and what mantle olivine actually is — around ninety per cent forsterite in most peridotite) → Forsterite

These are the most distinct paths back. Bauxite can be traced through others besides.

Downstream — what it becomes

Bauxite → is a source for (as a by-product of the Bayer process) → Gallium → is a source for (produced overwhelmingly in China, which introduced export controls in 2023 — a vulnerability that comes from the metal being somebody else's by-product rather than from any scarcity) → Gallium nitride → is used to make (as the high-electron-mobility transistor that has taken most of the high-power radio-frequency market — 5G base stations, radar and satellite transmitters) → Transistor → is used in (the component every other modern technology is assembled from, and one nobody ever sees) → Electronics manufacture → is associated with (and the supply chain it produced is the deepest and most concentrated in the world economy) → The semiconductor era complete chain
Bauxite → is used in (the only aluminium ore worked at scale) → Mining and quarrying → is associated with (steam pumping allowed mines below the water table, which is what made deep coal possible) → Industrial Revolution complete chain
Bauxite → is an ore of (via alumina — bauxite is refined by the Bayer process before smelting) → Aluminium → is an input to (the cheapest reducing metal and the commonest, and the aluminium in thermite) → Metallothermic reduction → produces (magnesium reducing boron oxide, which gives an impure amorphous boron — the crystalline element needs a different route entirely) → Boron → is a component of (about one per cent, and structurally essential — the compound is Nd₂Fe₁₄B, and without the boron it does not form) → Neodymium magnet → is used as (the strongest in commercial use, and the reason a motor, a hard drive and an earbud can be small) → Permanent magnets
Bauxite → is a source for (dissolved out with hot caustic soda in the Bayer process) → Aluminium oxide → is an input to (dissolved in molten cryolite and electrolysed) → Hall–Héroult process → produces (collects at the cathode while the carbon anodes are consumed) → Aluminium → is a component of (the base, and what the alloy exists to make useful) → Duralumin → is used as (aircraft structure, which it was developed for and dominated for half a century) → Structural engineering
Bauxite → is an input to (the ore, dissolved selectively so the iron and silica are left behind) → Bayer process → produces (crystallised from the liquor and calcined, ready for the smelter) → Aluminium oxide → is an input to (dissolved in molten cryolite and electrolysed) → Hall–Héroult process → produces (collects at the cathode while the carbon anodes are consumed) → Aluminium → is used as → Electrical conduction
Bauxite → is a component of (calcined, as the alumina source for the high-alumina grades) → Refractory brick → is an input to (or installed unfired as a monolithic castable and cured by the furnace's own first heat) → Firing → produces (as sintering, from refined powders rather than clay) → Technical ceramic → is used in (the honeycomb monolith the metals are dispersed across, which supplies the surface area and survives the thermal cycling) → Catalytic converter → is used as (the largest catalytic application by metal value there is) → Catalysis

These are the most distinct paths onward. Bauxite ends up in others besides.