Igneous Rocks are classified according to their origin, texture, and mineral composition. A rock that is formed from the cooling of molten rock. It is either magma below the surface or lava above the surface. ORIGIN: EXTRUSIVE ROCK INTRUSIVE ROCK Rock that is formed Rock that is formed inside Outside Ex. Basalt Ex. Granite (light in color) (Dark in color) TEXTURE FINE-GRAINED Glassy texture LARGE GRAINED large grain (coarse) IGNEOUS rocks form from “Red- Hot” and fiery molten material. What is the most common type of intrusive rock? Granite. What is the most common type of extrusive rock? Basalt Explain how the silica content of molten material affects the color of igneous rocks? Lava that is low in silica usually forms dark-colored rocks. Magma that is high in silica usually forms light-colored rock.