Basalt

Basalt is one of four categories of rocks found on the Moon with the others being pristine rocks, impact related rocks (breccias), and lunar soil. It is thought that the basalts of the Moon are a result of partial melting of the mantle just as they are on earth and rise to the surface because they are buoyant. As a group the Basaltic rocks are high in iron and titanium and tend to have a fine crystal structure as a result of rapid cooling.