Here's why:
* Igneous Rocks: Formed from the cooling and solidification of magma (underground) or lava (above ground). The type of magma/lava, cooling rate, and mineral composition all play a role.
* Sedimentary Rocks: Formed from the accumulation and cementation of sediments (fragments of other rocks, minerals, or organic material). The environment of deposition, the types of sediments, and the processes of weathering and erosion are crucial.
* Metamorphic Rocks: Formed when existing rocks (igneous, sedimentary, or even other metamorphic rocks) are transformed by heat, pressure, and/or chemically active fluids. The original rock type and the intensity and duration of the metamorphic processes are key factors.
Therefore, while factors like mineral composition, texture, and age are important characteristics of a rock, the process of formation is the defining aspect that determines its origin and properties.
