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n. A dark-green to black pyroxene mineral, (Ca,Na)(Mg,Fe,Al)(Si,Al)2O6, that contains large amounts of aluminum, iron, and magnesium.

n. A variety of pyroxene, usually of a black or dark green color, occurring in igneous rocks, such as basalt.

n. A variety of pyroxene, usually of a black or dark green color, occurring in igneous rocks, such as basalt; -- also used instead of the general term pyroxene.

n. The dark-green to black variety of pyroxene characteristic of basic eruptive rocks like basalt.

n. The name of this member of the pyroxene group of silicate minerals is frequently used in petrography in composition with the name of any rock in which it occurs as a prominent or noteworthy constituent: as, augite-andesite, augite-syenite, augite-gneiss, etc.

n. dark-green to black glassy mineral of the pyroxene group containing large amounts of aluminum and iron and magnesium

"Below this were strata of trachitic breccia and augite; the formation was then seamy to an unknown depth."

mineral   

feldspar    chrysoberyl    peridot    trachyte    whinstone    syenite    sard    hornblende    gneiss    breccia