Metamorphic Rocks

Metamorphic rocks are originated within the earths crust. Metamorphic rocks are created when both pressure and heat meet at the right time. During metamorphosis the rocks do not melt the heat and pressure just change the make-up of the rock. There are two types of metamorphosis low grade and high grade. Low grade metamorphosis occurs at 400 degrees C and 400MPa, while high grade is anything above 400 degrees c and 400MPa. Once the temperature reaches a little over 600 degrees Celsius and over 600MPa the rock then begins to melt and is no longer considered metamorphic.
The temperature and pressure will either cause the rocks minerals to re-crystallize forming new rock or it may cause a chemical reaction , which creates a new rock. Pore fluids are liquids found in the rocks pores. Pore fluids can increase the rate of re-crystallization and speed metamorphosis up by allowing the minerals to travel through the fluids and re-crystallize in another area more quickly. The pore fluids also can help the minerals by providing moisture for the minerals to grow and form with.
The two categories of metamorphic rock are foliated metamorphic rocks and non-foliated metamorphic rock. Foliated rocks are created from phylite and slate. These rocks may have a banded appearance and can be identified by their chemical make-up. Foliated metamorphic rocks are often fine grained and can have a make-up of many minerals.
Non-foliated metamorphic rocks are often made up of a single mineral or mostly of one mineral. Non-foliated metaphoric rocks are often called monomineralic, which means one mineral. The most common and known example of a monomineralic metamorphic rock would be marble. Marble is the metamorphic rock created after limestone has gone through the metamorphic process.