Orthopyroxenite
An orthopyroxenite is a rock made almost entirely of orthopyroxene, such as the Martian meteorite ALH 84001.
An orthopyroxenite is an igneous rock consisting mostly of orthopyroxene. On Earth such rocks form as cumulates in layered intrusions. Among meteorites, the most famous orthopyroxenite is ALH 84001, found in the Allan Hills of Antarctica in December 1984.
ALH 84001 is the oldest known Martian meteorite of its kind, crystallising about 4.1 billion years ago, and it is the only Martian orthopyroxenite. It contains small orange carbonate globules that formed later, roughly 3.9 billion years ago, from water moving through the rock on Mars. In 1996 a NASA team suggested features in these carbonates might be traces of ancient microbes. Later work showed non-biological processes could explain all of them, but the debate stimulated much research into Mars and life.
Diogenites from Vesta are also mainly orthopyroxenites. Orthopyroxenite as a name simply describes the rock; its origin is revealed by oxygen isotopes and chemistry.
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