Ohtaniite
A wadsleyite-like magnesium silicate with empty sites in its structure, crystallised from a shock melt of pyroxene composition.
Key facts
- Formula
- Mg3(Si0.5□0.5)Si2O8
- Family
- High-pressure minerals
- Crystal system
- Orthorhombic
- First described
- the Suizhou L6 chondrite, 2024
Ohtaniite was described in 2024 from the Suizhou L6 chondrite. It is named after Eiji Ohtani, a Japanese high-pressure mineralogist. It is known only from this meteorite.
What it is
Ohtaniite has the framework of wadsleyite, but with more silicon and with some of its metal sites left empty, so its overall recipe is close to that of pyroxene rather than olivine. Experiments had shown that wadsleyite can take up extra silicon in this way at high pressure; ohtaniite is the first natural example.
Where it is found
It crystallised in a shock-melt vein of the Suizhou chondrite, from melt or glass with the composition of low-calcium pyroxene, while the vein was still under high pressure.
How it is recognised
It is found by transmission electron microscopy and diffraction, which show the wadsleyite structure, combined with chemical analysis that shows its unusually high silicon.
Did you know?
Ohtaniite is one of the most recently named Suizhou minerals.
Empty sites in a mineral's structure are written with a small square in its formula.