By Anisa Noor
The Rock Cycle
How are Igneous, Sedimentary and metamorphic rocks classified?
Sedimentary rocks can be classified by forms; biological or chemical. Chemical was formed by evaporation or precipitation of sediments. Biological is formed as the result of biological activity millions of years ago. This includes all forms of animals and plants.
Metamorphic rocks are igneous and sedimentary rocks that have been put under a large amount of pressure and heat in the earths interior, so they tend to be harder and denser then most rocks.