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benmoreite An extrusive igneous rock consisting of anorthoclase, sodic plagioclase, ferroaugite (an iron-rich augite), and iron-rich olivine, and found as a member of the alkali basalt magma series. With increasing differentiation (see MAGMATIC DIFFERENTIATION) shown by increasing SiO2 content, the series is alkali basalt—hawaiite—mugearite—benmoreite—trachyte. The type locality after which the rock is named is Ben More on the Isle of Mull, Scotland.