The original igneous, sedimentary, or earlier metamorphic rock that get modified by heat, pressure, and chemical processes, hot mineral-rich fluids; some combination of these factors act usually while buried deep below Earth’s surface or where the tectonic plates meet. Exposure to these extreme conditions has altered the mineralogy, texture, and chemical composition of the rocks. All this leads to the formation of metamorphic rocks.
The main thing about metamorphic rocks is that they are shaped by great heat and pressure. The following traits are all related to that.
• Because their mineral grains grew together tightly during metamorphism, they’re generally strong rocks.
• They’re made of different minerals than other kinds of rocks and have a wide range of color and lustre.
• They often show signs of stretching or squeezing, giving them a striped appearance.
Some examples of metamorphic rocks are gneiss, slate, marble, schist, and quartzite.
There are two basic types of metamorphic rocks.
1.Foliated metamorphic rocks: such as gneiss, phyllite, schist, and slate have a layered or banded appearance that is produced by exposure to heat and directed pressure.
2.Non-foliated metamorphic rocks: such as hornfels, marble, quartzite, and novaculite do not have a layered or banded appearance.
The type of foliation that develops depends on the metamorphic grade. As slate is a very fine-grained, foliated metamorphic rock, characteristic of very low grade metamorphism, while phyllite is fine-grained and found in areas of low grade metamorphism, schist is medium to coarse-grained and found in areas of medium grade metamorphism, and gneiss coarse to very coarse-grained, found in areas of high-grade metamorphism.