Whitlockite
A calcium phosphate long confused with meteoritic merrillite.
Key facts
- Formula
- Ca9Mg(PO3OH)(PO4)6
- Family
- Phosphates
- Crystal system
- Trigonal
What it is
Whitlockite is a calcium magnesium phosphate that contains hydrogen. It is named after Herbert Whitlock, an American mineralogist. For decades, the hydrogen-free phosphate in meteorites and Moon rocks was called whitlockite too, until it was shown to be a different mineral, merrillite.
Where it is found
True whitlockite is rare in meteorites. Most reports of whitlockite in older meteorite literature refer to merrillite, which is common in chondrites, lunar rocks and Martian meteorites. Phosphates with some hydrogen, closer to true whitlockite, have been reported from a few samples, and the question is still studied.
How it is recognised
It can be told from merrillite only by careful analysis of hydrogen, or by spectroscopy and diffraction.
Did you know?
Whitlockite also forms in the human body, in some kinds of kidney stone.
The distinction from merrillite matters because hydrogen in phosphates is a clue to water.