Ferrihydrite
A poorly crystalline iron oxyhydroxide found in the matrix of CI chondrites.
Key facts
- Formula
- Fe10O14(OH)2
- Family
- Carbonates, sulphates, salts and weathering products
- Crystal system
- Hexagonal (poorly crystalline)
What it is
Ferrihydrite is a hydrous iron oxide with very small, poorly ordered crystals. It forms quickly where iron dissolved in water is oxidised, and over time it can turn into goethite or hematite. Its formula is only approximate.
Where it is found
It is common in the matrix of the Orgueil CI chondrite and in some other carbonaceous chondrites, often intergrown with clays. Part of it may have formed after the fall, as the meteorites reacted with air.
How it is recognised
It is identified by electron microscopy and spectroscopy, because its crystals are only a few nanometres across.
Did you know?
Ferrihydrite forms in the hearts of iron-storing proteins in the human body.
It is less common in Ryugu than in CI meteorites, another sign of change on Earth.