Magnesioferrite
A magnesium iron spinel that forms in cosmic spherules and fusion crusts.
Key facts
- Formula
- MgFe2O4
- Family
- Oxides
- Crystal system
- Cubic
What it is
Magnesioferrite is a spinel of magnesium and ferric iron. It is strongly magnetic. It forms where iron and magnesium are oxidised at high temperature.
Where it is found
It is common in cosmic spherules, micrometeorites that melted as they entered the atmosphere, where it forms tiny dendritic crystals, and in the fusion crusts of stony meteorites. Layers rich in magnesioferrite spherules mark some ancient impact horizons, including the one at the end of the Cretaceous.
How it is recognised
It forms black, feathery crystals in polished spherules, identified by microprobe analysis.
Did you know?
The composition of spinel in impact spherules shows how much oxygen was in the air when they formed.
A dense, post-spinel form of the same composition, maohokite, has been found at the Xiuyan crater in China.