gabbro

plural gabbros

1. countableuncountablegeographyOriginally, a kind of serpentine; now generally a coarsely crystalline, igneous rock consisting of lamellar pyroxene and labradorite.

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

   2022, Thomas Halliday, Otherlands, Penguin, published 2023, page 205

   1 more example

   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.

   2004, Richard Fortey, The Earth, Folio Society, published 2011, page 59