Basalt is an extrusivevolcanicrock that contains olivine and pyroxene minerals that make the rock dark-colored. It is usually fine-grained because of its rapid cooling of lava on the Earth's surface. Flood basalts are commonplace, formed by lava pouring out and solidifying.
Unweathered basalt is black or grey. Basalt blocks are often used for roads and pavements (sidewalks). It is hard-wearing and heat resistant.
On Earth, most basalt magmas have formed by melting of the mantle. Basalt has also formed on Earth's Moon, Mars, Venus, and even on the asteroid Vesta.