Gabbro belongs to a large group of mafic intrusive igneous rocks. Chemically very similar to basalt. Most of the Earth's crust is underlain by Gabbro in the oceanic crust, produced by basaltic magmatism at mid ocean ridges. It is also associated with continental volcanism. Gabbro is dense, greenish or dark-colored and contains pyroxene, plagioclase, and minor amounts of amphibole and olivine. This particular example comes from the Balmedie quarry near Aberdeen, Scotland. Specimens are supplied in labelled card trays.