Basalt: Igneous Rock - Pictures, Definition, Uses & MoreBasalt is an extrusive igneous rock. It is the bedrock of the ocean floor and also occurs on land in extensive lava flows.is basalt worth mining for,Basalt | Minerals Education CoalitionDescription. Basalt is a mafic (dark) igneous, extrusive volcanic rock. As such, basalt may be vesicular and brecciated. It is typically hard, tough and dense. Relation to Mining. Decorative basalt is occasionally handpicked from mining operations, and generally quarried cut and polished into tiles, slabs or other decorative.