Armalcolite
An iron–magnesium–titanium oxide named after the Apollo 11 astronauts.
Key facts
- Formula
- (Mg,Fe)Ti2O5
- Family
- Oxides
- Crystal system
- Orthorhombic
- First described
- Apollo 11 basalts, 1970
Armalcolite was described in 1970 from basalts collected by Apollo 11 in the Sea of Tranquillity. Its name is made from the first letters of the surnames of the crew: Armstrong, Aldrin and Collins. It was later found in rocks on Earth.
What it is
Armalcolite is an oxide very rich in titanium. It is stable only at high temperature and low pressure and tends to break down into ilmenite and rutile on slow cooling, so it survives in lavas that cooled quickly.
Where it is found
It is found in high-titanium lunar basalts, especially from Apollo 11 and Apollo 17, often as cores inside ilmenite crystals. On Earth it has been found in a few lavas and kimberlites.
How it is recognised
It forms grey, elongated crystals in polished section, distinguished from ilmenite by chemistry.
Did you know?
Armalcolite is the only mineral named after a spacecraft crew.
Its presence helps estimate how quickly lunar lava flows cooled.