Erg Chech 002 UNGROUPED
Classification: Achondrite (ungrouped, gabbroic with pyroxene megacrysts, sodic). Although the exsolved pigeonite in this meteorite is reminiscent of pyroxene in typical eucrites (with the notable exception of systematically much lower FeO/MnO ratios), the highly sodic and mildly potassic plagioclase is very different from the much more calcic plagioclase in eucrites (typically bytownite to anorthite, and only rarely as sodic as calcic labradorite Ab33An67). The cores of orthopyroxene megacrysts differ from typical diogenitic orthopyroxene in usually being more magnesian, more Cr-rich and having lower FeO/MnO ratios. Oxygen isotopes (Δ17O values) plot between the field for the majority of eucrites and the trend for angrites, in the vicinity of values for anomalous eucrites Bunburra Rockhole, Emmaville, Asuka 881394 and EET 92023. However, Erg Chech 002 is mineralogically quite different from those four meteorites in many respects, most notably the prevalence of highly sodic plagioclase and lower FeO/MnO ratios in pyroxenes.