Common volcanic rock is a type of igneous rock that is formed when molten lava cools and solidifies. The most common type of volcanic rock is BASALT, which is composed of plagioclase feldspar and pyroxene minerals. BASALT is a dark-colored, fine-grained rock that is usually found in the form of columns or hexagonal prisms. It is often used in construction and landscaping due to its durability and low cost.