Metamorphic rocks are broadly classified as foliated or non-foliated. Non-foliated metamorphic rocks do not have aligned mineral crystals. Non-foliated rocks form when pressure is uniform, or near the surface where pressure is very low.
How Are Metamorphic Rocks Classified?
Metamorphic rocks are rocks that have been subjected to extreme heat and pressure, resulting in a change in their physical and chemical composition. As a result, they are classified into different categories based on their origin, composition, and the temperatures and pressures they have been exposed to.
The first step in identifying metamorphic rocks is to look at their origin. This is because different types of rocks are formed under different conditions. Metamorphic rocks can be divided into two categories based on their origin: regional and contact. Regional metamorphic rocks form when preexisting rocks are exposed to regional metamorphic conditions, such as those that occur during mountain building processes. Contact metamorphic rocks form when preexisting rocks are exposed to metamorphic conditions due to the contact between hot igneous intrusions and the surrounding rocks.
The second step in the classification of metamorphic rocks is to look at their composition. Metamorphic rocks are composed of minerals that have been altered by heat and pressure. Common minerals found in metamorphic rocks include quartz, feldspar, mica, amphibole, and olivine. Other minerals, such as garnet and pyroxene, are also found in metamorphic rocks