Grove Mountains 99027

Antarctica

Found 2000 February 8

Martian meteorite (lherzolitic shergottite)

This meteorite weighs 9.97 g, and most of the surface is covered by fusion crust. Classification and mineralogy (Lin and B. Miao, GIG; H. Wang and C. Lin, NU): it is composed mainly of coarse-grained orthopyroxene, olivine, clinopyroxene and plagioclase, with minor opaque minerals. There are two textures. In the larger part of the sections, olivine occurs as rounded euhedral grains, poikilitically enclosed in a megacryst of orthopyroxene; in the other side of the sections, it shows a cumulate texture, consisting of euhedral orthopyroxene, clinopyroxene, olivine and interstitial plagioclase. Chromite, the most common opaque phase, is euhedral and enclosed in pyroxenes. The mineral assemblage and textures are similar to the Allan Hills (ALHA) 77005 lherzolite.  The FeO/MnO (wt%) ratio of orthopyroxene is 34 ± 5. Compositions of orthopyroxene (En66–78Fs20–26Wo2–8), clinopyroxene (En48–52Fs13–15Wo34–39), olivine (Fa22–30) and plagioclase (An49–55Ab44–50Or<1) overlap with the ranges in ALHA77005. Fracturing and undulose extinction in silicates are strong. Plagioclase is commonly deformed, and partially turns into maskelynite along the boundaries of grains. The shock stage is S4; weathering grade, W1. The meteorite is curated at PRIC.