Organic metamorphic rocks are a type of metamorphic rock that form from the transformation of organic materials, such as plant debris or other biological remains, under high temperature and pressure conditions. Unlike traditional metamorphic rocks that arise from the metamorphism of igneous or sedimentary rocks, these rocks are primarily composed of carbon-rich materials that originate from once-living organisms.
During the metamorphic process, the original organic material undergoes chemical and physical changes. This can lead to the formation of coal from plant material, which is often cited as a common example of an organic metamorphic rock, even though coal itself can be considered a sedimentary rock at certain stages of its formation. When subjected to even greater heat and pressure, coal can further metamorphose into anthracite, a higher-grade form of coal that exhibits distinct metamorphic characteristics.
In summary, organic metamorphic rocks highlight the interplay between biological processes and geological transformations, illustrating how organic materials can evolve over time under extreme conditions into rock forms that have distinct properties and uses.