Akimotoite
A high-pressure form of pyroxene with the ilmenite structure, formed in shocked meteorites.
Key facts
- Formula
- (Mg,Fe)SiO3
- Family
- High-pressure minerals
- Crystal system
- Trigonal
- First described
- the Tenham L6 chondrite, 1999
Akimotoite was described in 1999 from shock veins in the Tenham meteorite. It is named after Syun-iti Akimoto, a Japanese pioneer of high-pressure experiments.
What it is
Akimotoite has the chemistry of enstatite but the structure of ilmenite, with silicon surrounded by six oxygen atoms instead of four. It forms from pyroxene at pressures of about 20 to 25 gigapascals and temperatures lower than those needed for bridgmanite.
Where it is found
It occurs in and next to shock veins in heavily shocked L chondrites such as Tenham and Sixiangkou, usually as tiny grains replacing pyroxene.
How it is recognised
It is identified with electron microscopy and diffraction, or with Raman spectroscopy.
Did you know?
Silicon surrounded by six oxygens is rare at Earth's surface but normal in the deep mantle.
Tenham has yielded several high-pressure minerals new to science.