1. Igneous Rocks: Formed from the cooling and solidification of magma (molten rock) or lava.
* Intrusive igneous rocks: Form when magma cools and solidifies beneath the Earth's surface. Examples include granite, gabbro, and diorite.
* Extrusive igneous rocks: Form when lava cools and solidifies on the Earth's surface. Examples include basalt, rhyolite, and andesite.
2. Sedimentary Rocks: Formed from the accumulation and cementation of sediments, which are fragments of other rocks, minerals, or organic matter.
* Clastic sedimentary rocks: Formed from fragments of other rocks. Examples include sandstone, shale, and conglomerate.
* Chemical sedimentary rocks: Formed from the precipitation of minerals from water solutions. Examples include limestone, rock salt, and gypsum.
* Organic sedimentary rocks: Formed from the accumulation and decomposition of organic matter. Examples include coal and oil shale.
3. Metamorphic Rocks: Formed when existing rocks (igneous, sedimentary, or other metamorphic rocks) are transformed by heat and pressure.
* Foliated metamorphic rocks: Have a layered or banded appearance due to the alignment of minerals during metamorphism. Examples include slate, schist, and gneiss.
* Non-foliated metamorphic rocks: Do not have a layered appearance. Examples include marble, quartzite, and anthracite coal.
Important note: While igneous and metamorphic rocks make up the majority of the Earth's crust, sedimentary rocks are often the most visible on the surface because they are easily eroded and transported.
