Pyroxferroite
An iron-rich silicate that forms in the last melt of lunar and Martian basalts.
Key facts
- Formula
- (Fe,Ca)SiO3
- Family
- Silicates
- Crystal system
- Triclinic
- First described
- Apollo 11 basalts, 1970
Pyroxferroite was described in 1970 from Apollo 11 basalts. It has since been found in a few rocks on Earth and in lunar and Martian meteorites.
What it is
Pyroxferroite is a chain silicate similar in chemistry to iron-rich pyroxene but with a different structure. It is unstable at low pressure and temperature and slowly breaks down into fayalite, hedenbergite and silica, so it survives only in rocks that cooled quickly.
Where it is found
It occurs in late-stage pockets of lunar mare basalts and in some shergottites, often as rims on pyroxene.
How it is recognised
It is yellow to amber in thin section and identified by its iron-rich composition and crystal structure.
Did you know?
Its breakdown into a fine intergrowth of three minerals is called a symplectite, and it is common in lunar basalts.
Pyroxferroite is metastable: it should not exist where it is found, but it changes too slowly to disappear.