Main Page | See live article | Alphabetical index


Armalcolite is a mineral that was discovered at Tranquility Base on the Moon by the Apollo 11 crew in 1970. It was named for Armstrong, Aldrin and Collins, the three Apollo 11 astronauts. Examples of this mineral were later discovered in various locations on Earth as well, such as Smoky Butte, Garfield County, Montana (USA) in lamproite dykes and plugs, Disko Island (Greenland) in native iron, Pripyat Swell (Ukraine) in trachybasalt and in South African kimberlites.

It has a chemical formula of (Mg,Fe++)Ti2O5, a hardness of 6, and an orthorhombic crystal system. Armalcolite is a part of the pseudobrookite group which consists of minerals of the general formula X2YO5. X and Y are usually Fe (2+ and 3+), Mg, Al, and Ti. End members are armalcolite (MgFeTi2O5), pseudobrookite (Fe2TiO5), and ferropseudobrookite (FeTi2O5).