Basalt is a hard rock of volcanic origin and belongs to the group of extrusive rocks, which originate from the rapid cooling of lava exposed at or very near the surface of the earth. As opposed to this, granite forms of magma deep in the Earth's crust and appertains thus to the group of plutonic rocks. The material consists primarily of a mixture of iron and magnesium silicate with pyroxene and calcium-rich feldspar (plagioclase). The color of basalt varies usually between grey and black. Thanks to its excellent technical properties, basalt in most cases is suitable for applications, in- and outdoors.