Ferromerrillite
The iron-rich form of merrillite, the main phosphate of Martian shergottites.
Key facts
- Formula
- Ca9NaFe(PO4)7
- Family
- Phosphates
- Crystal system
- Trigonal
- First described
- Martian shergottites, 2016
Ferromerrillite was described in 2016 from Martian shergottites. It is the iron-dominant partner of merrillite and is known only from meteorites.
What it is
Ferromerrillite has the structure of merrillite, but with iron in the small metal site that merrillite fills with magnesium. Merrillite-group phosphates hold much of the phosphorus, and many of the rare earth elements, in meteorites.
Where it is found
It occurs in shergottites, basaltic rocks from Mars, where the late-crystallising melt was rich in iron. In shocked shergottites, merrillite-group phosphates can change into tuite, their high-pressure form.
How it is recognised
It is identified by microprobe analysis, which shows whether iron or magnesium dominates, and by X-ray diffraction.
Did you know?
The phosphates in Martian meteorites record the water and chlorine of Martian magmas.
Matyhite, from an angrite, is another iron-bearing member of the merrillite family.