Ferrihydrite
Ferrihydrite is a poorly crystalline iron oxyhydroxide found in CI chondrites and in rusting meteorites.
Ferrihydrite is an iron oxyhydroxide, a compound of iron, oxygen and water, so poorly crystalline that it is sometimes barely a mineral at all. It is common in soils and as a reddish-brown deposit in streams on Earth.
In CI chondrites it forms tiny grains within the clay-rich matrix, sometimes holding traces of nickel and phosphorus. Some is thought to have formed on the parent asteroid, but it can also grow when meteorites react with moist air, which makes it difficult to interpret in long-stored specimens.
Ferrihydrite is also an early product of the rusting of metal in meteorites found on Earth. It converts over time into more ordered iron oxyhydroxides such as goethite. Because its structure is so loose, it is studied with techniques such as transmission electron microscopy and X-ray absorption, rather than ordinary microscopes.
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