Armalcolite is a titanium-rich mineral

Mineral

A mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...

 with the chemical formula (Mg,Fe²⁺)Ti₂O₅. It was first found at Tranquility Base

Tranquility Base

Tranquility Base was the name given by American astronaut Neil Armstrong to the landing site on the moon where the Apollo 11 Lunar Module Eagle made the first moon landing....

 on the Moon

Moon

The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...

 in 1969 and named for Armstrong

Neil Armstrong

Neil Alden Armstrong is an American former astronaut, test pilot, aerospace engineer, university professor, United States Naval Aviator, and the first person to set foot upon the Moon....

, Aldrin

Buzz Aldrin

Buzz Aldrin is an American mechanical engineer, retired United States Air Force pilot and astronaut who was the Lunar Module pilot on Apollo 11, the first manned lunar landing in history...

 and Collins

Michael Collins (astronaut)

Michael Collins is a former American astronaut and test pilot. Selected as part of the third group of fourteen astronauts in 1963, he flew in space twice. His first spaceflight was Gemini 10, in which he and command pilot John Young performed two rendezvous with different spacecraft and Collins...

, the three Apollo 11

Apollo 11

In early 1969, Bill Anders accepted a job with the National Space Council effective in August 1969 and announced his retirement as an astronaut. At that point Ken Mattingly was moved from the support crew into parallel training with Anders as backup Command Module Pilot in case Apollo 11 was...

 astronauts. Together with tranquillityite

Tranquillityite

Tranquillityite is silicate mineral with an average formula 82Ti33O4. It is mostly composed of iron, oxygen, silicon, zirconium and titanium with smaller fractions of yttrium and calcium. It is named after the Mare Tranquillitatis , the place on the Moon where it was found during the Apollo 11 and...

 and pyroxferroite

Pyroxferroite

Pyroxferroite SiO3 is a silicate mineral of the pyroxene group. It is mostly composed of iron, silicon and oxygen, with smaller fractions of calcium and several other metals. Together with armalcolite and tranquillityite, it is one of the three minerals which were discovered on the Moon. It was...

, it is one of the three minerals which were discovered on the Moon. Armalcolite was then identified in various locations on Earth and synthesized in the laboratory.