About Basalt Blocks : Basalt is an extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron exposed at or very near the surface. More than 90% of all volcanic rock on Earth is basalt. It has a composition similar to gabbro. At this link of Stonemarket.online, you can find rough blocks and various size boulders of basalt and lava stone, their owners, basalt rock composition and the most reasonable prices, which are mined in various parts of the world.