* Igneous rocks are formed from the cooling and solidification of magma (molten rock) or lava. Examples include granite, basalt, and obsidian.
* Sedimentary rocks are formed from the accumulation and cementation of sediments, which are fragments of other rocks, minerals, or organic materials. Examples include sandstone, limestone, and shale.
While metamorphic rocks are also found in the Earth's crust, they are formed from existing igneous or sedimentary rocks that have been transformed by heat, pressure, or chemical reactions.
