Rocks are naturally occurring solids which are composed of minerals & have been used by humans since ages. From Stone Age, rocks are used for various purposes. Also, the metals and minerals found in rock play an important role in our life. Get to know all the Basalt Uses. We have provided you with all information about Basalt rock here. Basalt is a common extrusive igneous rock formed by the rapid cooling of basaltic lava exposed at or very near the surface of Earth. Basalt is available in black, brown, light to dark grey colors. The streak of a rock is the color of powder produced when it is dragged across an unweathered surface. The streak of Basalt is white to grey. Get to know more about Basalt rock and characteristics of Basalt rock in the next sections.