Which type of rock is classified as metamorphic?

Metamorphic rocks are formed under conditions of high pressure and temperature that cause physical and chemical changes to pre-existing rocks. These parent rocks can be igneous, sedimentary, or even other metamorphic rocks. Slate is classified as a metamorphic rock because it originates from shale, a sedimentary rock, through the process of metamorphism. During this process, the shale undergoes changes in mineral composition and texture due to increased heat and pressure, resulting in a fine-grained rock with excellent fissility and the ability to break into thin layers. This characteristic makes slate a prime example of metamorphic rock.

In contrast, limestone is a sedimentary rock primarily composed of calcite, peat is an accumulation of organic material that can eventually turn into coal, and sandstone, also a sedimentary rock, consists mainly of sand-sized minerals or rock grains. Understanding the classification of rock types helps in various fields of environmental science, geology, and earth sciences.