Its red sands are also full of iron, turned to rust by atmospheric oxygen.

NEWYORKER: The Martian Chroniclers

Like other iron minerals, green rust readily absorbs dissolved elements onto its surface, but green rust is not only particularly efficient at this in many cases, it can also react with toxic dissolved trace metals to make them insoluble, and as a result, renders them in nontoxic forms.

MSN: What green rust did long ago to the big blue ocean

This liberates hydrogen ions for the acidity, turns insoluble sulfide into very soluble sulfate, and creates rust from reduced iron, a fascinating, if annoying, chemical process.

FORBES: Fracking With Bad Water

Over millions of years this created an oxygen-rich atmosphere that rapidly removed electrons from minerals near the surface, creating rust out of iron and forming thousands of new minerals from other metals like nickel, copper and uranium.

ECONOMIST: Minerals

Rust is the metal (Fe for iron) turning to the oxide (Fe2O3 normally for iron although there are other oxides).

FORBES: Will Handling Your iPhone 5 Damage It? Maybe...

Eventually they'll be brought back and reattached to the Cutty Sark's iron frame after it has been specially treated for rust.

BBC: NEWS | UK | Cutty Sark rises from the ashes

Here, the deep burnt sienna red of the soil - rust-coloured because of its richness in iron - mingles with thickets of foliage and a sweep of clear sky.

BBC: The three colours of Ibiza

As the bacteria produced oxygen, the two compounds reacted to form iron oxide, which precipitated onto the seafloor in great layers of rust.

NEWYORKER: The Martian Chroniclers

If anything, the soil seemed inimical to life: there was so much iron in it that any whiff of oxygen was quickly bound into rust.

NEWYORKER: The Martian Chroniclers

The roof was iron, and it looked to be sound, though storm-dented and running with rust.

NEWYORKER: Idols