Science / Geology / Gabbro: A black, coarse-grained intrusive igneous rock that is the compositional equivalent of basalt. Composed of calcium-rich feldspars, pyroxene and possibly olivine, but containing little if any quartz. Picture of Gabbro.


Science / Geology / Mafic: A term used to describe an igneous rock that has a large percentage of dark-colored minerals such as amphibole, pyroxene and olivine. Also used in reference to the magmas from which these rocks crysta MORE


Science / Geology / Basalt: A dark-colored fine-grained extrusive igneous rock composed largely of plagioclase feldspar and pyroxene. Similar in composition to gabbro. Basalt is thought to be one of the main components of oceani MORE

Basic Rock

Science / Geology / Basic Rock: An igneous rock that has a relatively low silica content. Examples are gabbro and basalt. Also see entries for acidic, intermediate and ultrabasic rocks. MORE

Ophiolite Suite

Science / Geology / Ophiolite Suite: The typical sequence of rocks in the oceanic crust from bottom to top: ultrabasic rocks, gabbro, sheeted dikes, pillow basalts, and sea-floor sediments. Igneous rocks and deep-sea sediments associated MORE