Basalt is an extrusive, dark-coloured, aphanitic (fine grained) igneous rock mainly composed of plagioclase feldspar and pyroxene. It has a chemical composition similar to Gabbro, but it’s not coarse grained like this last one is. It is formed when basaltic lava near Earth’s surface rapidly cools down into a crystallized structure, usually black in colour, but subject to assume brown or rust-red colours due to the oxidation of some of its minerals.
This is Earth’s most common volcanic rock, found in oceanic crust as well as in some oceanic islands. Basalt has a characteristic texture, formed when gases come out of the original lava and forms bubbles, and when they are trapped inside the magma, cooling down to a solid rock before they can escape.
Because of its properties, Basalt is used mostly in construction, making cobblestones and statues. It also can produce stone wool when it undergoes heating and extrusion, and can be used as grinding stone for grains. In the Mohs hardness scale, it scores around 6, thanks to its feldspar composition.
The Stone Wiz 