* Igneous Rocks: Formed from the cooling and solidification of molten rock (magma or lava). Examples: granite, basalt, obsidian.

* Sedimentary Rocks: Formed from the accumulation and cementation of sediments, such as sand, mud, or organic debris. Examples: sandstone, limestone, shale.

* Metamorphic Rocks: Formed when existing rocks (igneous, sedimentary, or even other metamorphic rocks) are transformed by heat, pressure, or chemical reactions. Examples: marble, slate, gneiss.