Basalt is an igneous rock, formed during volcanic eruptions from the hot lava coming out of a volcano. Basalt is very dark in color that is made of many dark colored minerals such as pyroxene and olivine. Basalt also contains some light colored minerals such as feldspar and quartz, but the amounts are small. Typically, you can't see most of the mineral crystals without using a microscope because quick cooling prevents large crystals from forming. Like other stones, basalt is an age-old material, probably best known to most of us in the form of cobblestone paving of roads and pathways. In recent years it has seen a revival of sorts in the redevelopment of residential streets and pedestrians malls.