gabbro

noun

1. (countable, uncountable)Originally, a kind of serpentine; now generally a coarsely crystalline, igneous rock consisting of lamellar pyroxene and labradorite.

   “It is known as gabbro and is thought to form the lower layer of the oceanic crust at about four kilometres depth and to comprise a layer up to six kilometres thick, making it one of the most abundant, if least recognisable, materials on earth.”

   “Against the dark Ordovician gabbro, the black volcanic base, Rhynie is a streak of technicolour.”