Diabase

Di′a·base, n. [F. diabase, fr. Gr. διάβασις a crossing or passing over, fr. ?; ? + βαίνειν to go; — so called by Brongniart, because it passes over to diorite.] (Min.) A basic, dark-colored, holocrystalline, igneous rock, consisting essentially of a triclinic feldspar and pyroxene with magnetic iron; — often limited to rocks pretertiary in age. It includes part of what was early called greenstone.