A dark, fine-grained igneous rock that forms from the cooling of lava or magma, commonly used in construction and paving.
From Greek diabasis (passage or crossing), from diabainein (to go through). Named in German as 'Diabas' in the 18th century because it was thought to form a transition between different rock types.
Diabase is literally everywhere—it paves many roads, lines railroad beds, and makes up important parts of the Earth's ocean floor, yet most people never learn its name because it's so ordinary.
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