Grossmanite
A pyroxene containing titanium in an unusual state, found in the oldest inclusions in Allende.
Key facts
- Formula
- CaTiAlSiO6
- Family
- Silicates
- Crystal system
- Monoclinic
- First described
- the Allende CV3 chondrite, 2009
Grossmanite was described in 2009 from a calcium-aluminium-rich inclusion in the Allende meteorite. It is named after Lawrence Grossman, who worked out how minerals condense from a cooling solar gas.
What it is
Grossmanite is a pyroxene in which titanium carries a charge of three, Ti³⁺, rather than the usual four. Titanium of that kind survives only where oxygen was extremely scarce, as in the hot gas of the solar nebula.
Where it is found
It is the titanium-rich end member of the pyroxene once called fassaite, found in type B CAIs of CV chondrites. It also occurs in some other carbonaceous chondrites.
How it is recognised
It is identified by microprobe analysis and electron backscatter diffraction. Its pale purple to brown colour in thin section comes from the titanium.
Did you know?
The ratio of Ti³⁺ to Ti⁴⁺ in CAI pyroxenes is used to estimate how much oxygen was in the gas where they formed.
Lawrence Grossman's condensation calculations predicted many of the minerals found in CAIs.