Question

How is foliated metamorphic rock different from a non-foliated metamorphic rock?

Answer 1

Hint: Rocks are solid masses that are made up of minerals and mineraloid matter and there are three main categories of it based on the process of their formation— igneous, sedimentary and metamorphic. Rocks form the crust of the earth and both the upper and lower mantle. Metamorphic rocks, as the name suggests, are formed due to the process of metamorphism which entails changes in the minerals and geological texture of pre-existing rocks due to heat and pressure. Around 12% of the earth’s surface is made up of metamorphic rocks.

Complete answer: Although all foliated and nonfoliated metamorphic rocks are derived from igneous or sedimentary rocks, the process of recrystallisation makes them different. Foliated rock is formed as a result of unequal pressure is applied during recrystallisation while a non-foliated rock is formed when equal pressure is applied during the same. Foliated rocks break or separate into peels and thin layers and are made up of finer particles. On the other hand, non-foliated rocks have a granular appearance because they are made up of coarse grains. Examples of foliated rocks include slate, phyllite, schist, gneiss, etc and examples of non-foliated rocks include marble, quartzite, hornfels, anthracite coal, etc.

Note: Igneous rocks are made up of solidified lava and magma which may either penetrate existing rocks and crystallise or erupt during volcanic activity and cool down over time to form rocks. Sedimentary rocks are formed due to the accumulation of minerals and organic matter in layers on top of each other over time.