Fluorapatite
The fluorine-rich member of the apatite group, important in Martian and lunar meteorites.
Key facts
- Formula
- Ca5(PO4)3F
- Family
- Phosphates
- Crystal system
- Hexagonal
What it is
Fluorapatite is a calcium phosphate with fluorine. It belongs to the apatite group, in which fluorine, chlorine and hydroxyl swap places; tooth enamel is a close relative. The amounts of these in a grain record the water and halogens of the melt it grew from.
Where it is found
It is the common apatite in lunar basalts and occurs in some Martian shergottites, in eucrites and in ordinary chondrites alongside chlorapatite and merrillite.
How it is recognised
It is colourless, with six-sided crystals, and is told apart from chlorapatite by microprobe analysis.
Did you know?
Hydrogen in lunar apatite helped overturn the old idea that the Moon is completely dry.
Fluoride toothpaste works by turning some enamel into fluorapatite, which resists acid better.