what is basalt
/bÉËsÉËlt/ , /ËbaesÉlt/ , /ËbÃ¦sÉlt/ , ËbaesÉËlt /ËbÃ¦sÉËlt/) or ËbeÉªsÉËlt is a common (extrusive) igneous volcanic rock formed from the rapid cooling of basaltic lava exposed at or very near the surface of a planet. Or moon flood basalt describes the formation in a series of lava. basalt flowsy definition, basalt is an aphanitic igneous rock with less than 20% quartz and less than 10% feldspathoid by volume, and where at least 65% of the feldspar is in the form of plagioclase.