* Igneous Rocks: Formed from the cooling and solidification of magma (molten rock) or lava. Examples include granite, basalt, and obsidian.
* Sedimentary Rocks: Formed from the accumulation and cementation of sediments (fragments of other rocks, minerals, or organic matter). Examples include sandstone, limestone, and shale.
* Metamorphic Rocks: Formed when existing rocks (igneous, sedimentary, or other metamorphic rocks) are transformed by heat, pressure, or chemical reactions. Examples include marble, slate, and gneiss.
While the mineralogy (the types of minerals present) and texture (the size, shape, and arrangement of mineral grains) are also important factors in classifying rocks, they are secondary to the mode of formation.
