A dark-gray to black, fine-textured igneous rock composed mainly of feldspar and pyroxene and used for monuments and as crushed stone.
[From French diabase, originally meaning “diorite,” (now “basalt or gabbro lightly modified by metamorphism”), coined by French mineralogist Alexandre Brongniart (1770-1847), probably from Greek diabasis, a crossing over (from diabainein, to pass through or over; see DIABETES; the rock being so called because it is often found as intrusive sills and dikes in other rocks), or perhaps an alteration of an intended French *dibase (di-, two, from Greek di-; see DI-1 + base, basis, from Old French; see BASE1; the rock being so called in reference to feldspar and amphibole, two important constituent minerals of diorite).]
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