IGNEOUS ROCKS Igneous rocks are one of the three main rock types, alongside sedimentary and metamorphic rocks. They form through the cooling and solidification of molten material, either magma beneath the Earth’s surface or lava at the surface. The term igneous comes from the Latin word ignis, meaning fire. FORMATION When magma cools slowly beneath the Earth’s crust, it produces intrusive (plutonic) igneous rocks with large, visible crystals. When lava cools rapidly on the surface, it forms extr