A rock is a naturally occurring solid mass or aggregate composed of minerals or mineraloid matter. It forms the Earth's solid outer layer (the crust) and can also be found inside the Earth, except in the liquid outer core and magma pockets. Rocks are primarily made of mineral grains, which are crystalline solids with an orderly atomic structure, but they can also include mineraloids such as volcanic glass and organic materials like fossils or decomposed plant matter in coal
. Rocks are classified into three main types based on their formation processes:
- Igneous rocks: Formed by the cooling and solidification of molten material called magma or lava.
- Sedimentary rocks: Formed by the deposition, burial, compression, and cementation of fragments from preexisting rocks or by precipitation of minerals from solutions.
- Metamorphic rocks: Formed when existing rocks are transformed by high heat and pressure without melting, altering their mineral composition and texture
In summary, a rock is a solid geological material made up of one or more minerals or mineraloids, classified mainly into igneous, sedimentary, and metamorphic types according to how they form
