Armalcolite
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Mineral NameArmalcolite
Chemical Formula(Mg,Fe2+)Ti2O5
Mohs Hardness5.5
Crystal Systemorthorhombic
Lustermetallic
Streak Colorgray-black
Cleavagepoor on {110}
Fractureuneven
Specific Gravity4.15
Colorsblack, dark gray, brownish-black
Transparencyopaque
Type LocalityTranquility Base, Moon (Apollo 11 landing site)
Mineral GroupOxides
Usesscientific research, collector
Associated Mineralsilmenite, rutile, pyroxene, olivine, plagioclase
Rarityrare
Description
Armalcolite is an opaque, dark gray to black mineral, typically found as small grains or tabular crystals with a metallic to submetallic luster.
Geological Context
This high-temperature, low-pressure mineral was first discovered in lunar basalts and is also found in some terrestrial ultramafic rocks and meteorites, forming under specific igneous conditions.
