diabasic

Diabasic refers to a mafic igneous rock that is compositionally equivalent to basalt but is typically coarser-grained, exhibiting a ophitic or subophitic texture. This texture is characterized by lath-shaped plagioclase feldspar crystals that are partially or completely enclosed by larger pyroxene crystals. Diabase is an intrusive rock, meaning it solidifies from magma that has intruded into pre-existing rock formations beneath the Earth's surface. It commonly occurs in dikes, sills, and laccoliths, which are tabular or mushroom-shaped intrusions.

The mineral composition of diabase is primarily composed of calcic plagioclase feldspar (labradorite to bytownite) and pyroxene, usually augite. Olivine may also be present, and accessory minerals like magnetite, ilmenite, and sometimes quartz can occur. Its color is typically dark gray to black, owing to the abundance of mafic minerals. Diabase is known for its toughness and resistance to weathering, making it a durable building material, historically used for pavements, curbstones, and decorative elements. It is also a common rock type found in the oceanic crust and in large igneous provinces. The formation of diabase is often associated with rifting events and continental breakup, where magma wells up to fill fractures in the crust.