Asimowite
The iron-rich partner of wadsleyite: a dense form of fayalite made by shock.
Key facts
- Formula
- Fe2SiO4
- Family
- High-pressure minerals
- Crystal system
- Orthorhombic
- First described
- the Suizhou L6 and Quebrada Chimborazo 001 CB3 chondrites, 2019
Asimowite was described in 2019 from the Suizhou L6 chondrite and the Quebrada Chimborazo 001 CB chondrite from Chile. It is named after Paul Asimow, an American geochemist who studies how rocks behave in impacts. It is known only from meteorites.
What it is
Asimowite has the structure of wadsleyite, the high-pressure form of olivine stable in Earth's upper mantle, but with iron in place of magnesium. Iron-rich olivine normally turns straight into the spinel form ahrensite under pressure, so a natural wadsleyite-type iron silicate was a surprise. It probably grew quickly and out of equilibrium during the brief shock pulse.
Where it is found
It occurs as tiny grains in and around shock-melt veins, where iron-rich olivine was squeezed and heated, in the Suizhou L6 chondrite and in Quebrada Chimborazo 001, a metal-rich CB chondrite.
How it is recognised
It is identified by electron microscopy and diffraction, together with an electron microprobe analysis showing that iron, not magnesium, fills most of its metal sites.
Did you know?
Asimowite and ahrensite are the iron partners of wadsleyite and ringwoodite.
Its discovery suggests that shock can produce minerals that never form under steady pressure.