|1.||See flood basalt a fine-grained dark basic igneous rock consisting of plagioclase feldspar, a pyroxene, and olivine: the most common volcanic rock and usually extrusive|
|2.||a form of black unglazed pottery resembling basalt|
|[C18: from Late Latin basaltēs, variant of basanītēs, from Greek basanitēs touchstone, from basanos, of Egyptian origin]|
|basalt (bə-sôlt', bā'sôlt') Pronunciation Key
A dark, fine-grained, igneous rock consisting mostly of plagioclase feldspar and pyroxene, and sometimes olivine. Basalt makes up most of the ocean floor and is the most common type of lava. It sometimes cools into characteristic hexagonal columns, as in the Giant's Causeway in Anterim, Northern Island. It is the fine-grained equivalent of gabbro.
A hard, dense igneous rock that makes up much of the material in tectonic plates. The part of the Earth's crust beneath the oceans consists mainly of basalt whereas continental crust consists mainly of less dense rocks, such as granite. (See plate tectonics.)