Diabase (or dolerite) is a medium-grained igneous rock with basaltic composition. The term is also synonym of microgabbro. The name comes from the Greek diabasis, meaning ‘crossing over’, which is appropriate since this rock is texturally halfway between a gabbro and a basalt. Dolerite has a similar origin, from the Greek doleros, deceptive. Diabase are subvolcanic rocks and are found in hypoabissal igneous bodies, such as small intrusions or dykes.