Gabbro 2 : A coarse-grained rock composed of greenish-white feldspar (mostly plagioclase) and pyroxene. Gabbro is usually very dark in color. It is the intrusive equivalent of basalt. An intrusive igneous rock. (Plank and Schenck, 1998)
U.S. Department of the Interior, U.S. Geological Survey, US Geological Society (USGS), Glossary of Volcano and Related Terminology, USGS/Cascades Volcano Observatory, Vancouver, Washington, USA 2006. http://vulcan.wr.usgs.gov/Glossary/volcano_termino logy.html, (ND/ Volc Sci - Amer) {493}