Armalcolite

Armalcolite is a mineral that was discovered at Tranquility Base on the Moon by the Apollo 11 crew in 1969. It was named for Armstrong, Aldrin and Collins, the three Apollo 11 astronauts. Examples of this mineral were first identified on Earth within three years by geologist Danielle Velde from samples of lamproite dikes and plugs taken in Smoky Butte, Garfield County, Montana, USA[1]. Other examples were later identified in: Disko Island, (Greenland) in native iron; Pripyat Swell (around the Pripyat River, Ukraine) in trachybasalt and in South African kimberlites.

Armalcolite has a chemical formula of (Mg,Fe⁺⁺)Ti₂O₅. It has a Mohs hardness of 6 and a specific gravity of 4. It forms grey sub to anhedral masses with a crystal structure that is orthorhombic prismatic. 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 ((MgFe)Ti₂O₅), pseudobrookite (Fe₂TiO₅), and ferropseudobrookite (FeTi₂O₅).

References

1. ^ Armalcolite-Ti-Phlosopite-Diopside-Analcite-Bearing Lamproites Armalcolite-Ti-Phlosopite-Diopside-Analcite-Bearin from Smoky Butte, Garfield County, Montana, D. Velde, American Mineralogist, Volume 60, pages 566-573, 1975, accessed 04/05/2010

* Webmineral data
* Mindat with location data
* Mineral Data Publishing PDF



List of minerals