Goethite
Goethite is an iron oxyhydroxide that forms the brown rust on weathered meteorites.
Goethite is an iron oxyhydroxide, FeO(OH), named after the German writer Johann Wolfgang von Goethe, who had a keen interest in minerals. It is brown to yellow-brown and is one of the main components of rust.
When a meteorite sits on Earth's surface, water and oxygen attack its iron-nickel metal and iron sulfide. The first products are often unstable minerals such as akaganeite and ferrihydrite, which gradually change to goethite and other iron oxides. Brown staining that spreads from metal grains through a stony meteorite is largely goethite, and it is the basis of the weathering grades W0 to W6 used to describe how rusted a meteorite is.
Goethite fills cracks and expands as it grows, so it can split a meteorite apart over time. On iron meteorites, a thick goethite and magnetite crust can build up. Its presence is a sign of terrestrial age and of the need for dry storage.
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Level: Explorer Ages 10 and up