An aphanitic (fine-grained) igneous rock is classified as basalt when its QAPF fraction is composed of less than 10% feldspathoid and less than 20% quartz, and plagioclase makes up …

Apr 10, 2018 · Basalt is the most abundant volcanic rock on Earth, covering more than 90% of the ocean floor and large continental regions shaped by ancient lava flows. It forms when mafic …

Basalt is a dark-colored, fine-grained, igneous rock composed mainly of plagioclase and pyroxene minerals. It most commonly forms as an extrusive rock, such as a lava flow, but can also form …

Nov 12, 2025 · Basalt, extrusive igneous (volcanic) rock that is low in silica content, dark in color, and comparatively rich in iron and magnesium. Basalts may be broadly classified on a …

Basalt is defined as a fine-grained, dark-colored igneous rock composed mainly of plagioclase and pyroxene minerals, with or without olivine. It is formed from the rapid cooling of basaltic …

Aug 17, 2023 · Basalt is a common and widely used, fine-grained, dark-colored mafic volcanic rock. It has mainly calcic plagioclase feldspar and augite.

Dec 14, 2012 · Basalt is a very common dark-colored volcanic rock composed of calcic plagioclase (usually labradorite), clinopyroxene (augite) and iron ore (titaniferous magnetite). …

Basalt and related rock types like andesite and dacite are rocks that form when volcanoes erupt magma (lava) onto the surface of the earth and the magma cools. Basalt flows on Hawaii.

Basalt is a hard, black volcanic rock with less than about 52 weight percent silica (SiO2). Because of basalt's low silica content, it has a low viscosity (resistance to flow). Therefore, basaltic lava …

Jul 25, 2025 · Discover basalt rock—Earth's dark, fine‑grained volcanic workhorse. See how it forms, where to find it, and its many uses from roads to rock‑wool insulation.