1. Parent Rock:
* Protolith: The original rock before metamorphism is a key factor. Many metamorphic rocks are named after their protolith, often with a prefix indicating the metamorphic change.
* Example: Marble is named after the protolith limestone.
* Example: Slate is named after the protolith shale.
2. Texture:
* Foliation: Many metamorphic rocks develop a layered or banded texture due to pressure during metamorphism. The type of foliation can influence the name.
* Example: Schist has a distinct, flaky foliation.
* Example: Gneiss has a banded foliation with alternating light and dark layers.
* Non-Foliated: Rocks that don't develop foliation are often named based on their mineral composition or other features.
3. Mineral Composition:
* The type and arrangement of minerals present in a metamorphic rock are crucial for identification and naming.
* Example: Amphibolite is named after the presence of amphibole minerals.
* Example: Quartzite is named after the dominant mineral, quartz.
4. Degree of Metamorphism:
* The intensity of heat and pressure during metamorphism impacts the resulting rock. This can be reflected in the name.
* Example: "Low-grade" metamorphic rocks, like slate, form under less intense conditions.
* Example: "High-grade" metamorphic rocks, like gneiss, form under higher temperatures and pressures.
5. Other Features:
* Some metamorphic rocks are named after distinctive features or origins.
* Example: Migmatite is a rock formed from the mixing of igneous and metamorphic components.
* Example: Eclogite is named after its unusual mineral assemblage, found only at very high pressures.
In Summary:
Metamorphic rock names are derived from a combination of their parent rock, texture, mineral composition, degree of metamorphism, and other unique features. This helps to classify and describe the diverse array of metamorphic rocks found in the Earth's crust.
