The term 'Lava Rock' is a common name for the igneous rock known as BASALT, which has six letters. BASALT is an extrusive igneous rock that forms when molten lava cools and solidifies on the surface of the Earth. It is composed mainly of plagioclase and pyroxene minerals and is usually black or dark gray in color. BASALT is the most common type of rock in the Earth's crust and is found in many locations around the world.