ALH 84001 is an extraterrestrial example of an orthopyroxenite. It is an achondrite meteorite from Mars.

Orthopyroxenite is an ultramafic and ultrabasic rock that is almost exclusively made from the mineral orthopyroxene, the orthorhombic version of pyroxene and a type of pyroxenite. It can have up to a few percent of olivine and clinopyroxene.

This ternary diagram shows the orthopyroxenites as a function of olivine, clinopyroxene and orthopyroxene abundance.

Orthopyroxenites can also occur on other planets. ALH 84001 is a Martian meteorite that can be classified as an orthopyroxenite. It is the only meteorite found with that composition and the only member of the Martian orthopyroxenite group of meteorites.^[1]

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