CoachAn igneous rock forms when molten rock cools and becomes solid: granite deep underground, basalt from lava. A sedimentary rock forms at the Earth’s surface from grains of sand and mud, or from the shells of living things, laid down in layers and then hardened: sandstone, shale, limestone. A metamorphic rock is a rock that has been transformed, without melting, by heat and pressure deep underground: marble (from limestone), slate (from shale).
