Types of Rocks formed when heat or pressure is added composition and texture, resulting in the formation of metamorphic rocks. Metamorphic rocks are classified based on their texture and mineral composition. Here are the main types of metamorphic rocks formed under heat and pressure:
Three types of rocks
There are three types of rocks that are studied in Geography and Geology, which are:
- Sedimentary rocks,
- Igneous rocks and
- Metamorphic rocks.
Rocks are classified based on the way they form.
How Metamorphic rocks form
Out of the three rocks types, metamorphoric rocks are the ones that only form when rocks are subjected to high heat, high pressure, hot mineral-rich fluids or, more commonly, some combination of these factors.
Here are the main types of metamorphic rocks formed under heat and pressure:
- Slate:
- Texture: Fine-grained
- Parent Rock: Shale
- Formation: Low-grade metamorphism of shale
- Schist:
- Texture: Medium to coarse-grained
- Parent Rock: Shale, phyllite, or other schists
- Formation: Intermediate to high-grade metamorphism
- Gneiss:
- Texture: Coarse-grained, banded
- Parent Rock: Granite, shale, or schist
- Formation: High-grade metamorphism
- Marble:
- Texture: Non-foliated, granular
- Parent Rock: Limestone or dolostone
- Formation: Metamorphism of carbonate rocks
- Quartzite:
- Texture: Non-foliated, granular
- Parent Rock: Sandstone
- Formation: Metamorphism of sandstone
- Phyllite:
- Texture: Fine-grained, sheen or glossy appearance
- Parent Rock: Slate
- Formation: Intermediate-grade metamorphism
- Anthracite Coal:
- Texture: Non-foliated
- Parent Rock: Bituminous coal
- Formation: High-grade metamorphism of coal
- Hornfels:
- Texture: Fine-grained, typically lacks foliation
- Parent Rock: Various rocks (igneous, sedimentary, or other metamorphic rocks)
- Formation: Contact metamorphism due to high temperatures from nearby molten rock (magma)
Conclusion
Metamorphic rocks form as a result of the alteration of pre-existing rocks (called parent rocks) under the influence of heat and/or pressure. The specific type of metamorphic rock that forms depends on factors such as the intensity of heat and pressure, mineral composition of the parent rock, and the presence of fluids during the metamorphic process.