The above metamorphic rocks represent some of the basic types that can be found in the field. There are other types of metamorphic rocks that form from different parent rocks. Many of these are named based on the mineral composition of the parent rock. When limestone is subjected to heat and pressure, it changes to marble. When sandstone or chert is metamorphosed, the result is called quartzite. Other metamorphic rocks include hornfels, a fine-grained rock formed from mudstone and basalt and amphibolite, a high grade metamorphic rock formed from basalt. Serpentinite is composed almost entirely of the mineral serpentine.
Metamorphic rocks form in a variety of manners, generally the result of regional changes in temperature and pressures, or the result of contact with an igneous intrusion. Metamorphic rocks are named based on the structural and mineralogical changes that occur as a result of the metamorphism. Although they are harder to name, once a geologist understands how temperature and pressure affects a rock, naming metamorphic rocks can become relatively easy.
Glossary
Amphibolite: High grade foliated metamorphic rock made from basalt.
Contact Metamorphism: Type of metamorphism that occurs when igneous intrusions make contact with existing rock.
Diagenesis: Physical and chemical processed that turn unconsolidated sediment into a sedimentary rock.
Facies: The temperature and pressure conditions under which they were metamorphosed.
Gneiss: Metamorphic rock that contains coarse bands of differing textures and minerals.
Hornfels: A fine-grained rock formed from mudstone and basalt.
Marble: Metamorphic rock composed entirely of calcitic or dolomitic limestone.
Metamorphic Rocks: Any rock that results from extensive changes to texture and mineralogy of the parent rock.
Phyllite: Silky, foliated rock generally more coarsely grained than slate.
Quartzite: Rock which results from the metamorphism of sandstone or chert.
Regional Metamorphism: Type of metamorphism that occurs over large geographic areas, generally the result of mountain building events.
Schist: Metamorphic rock with visible mineral crystals and still able to be split into thin slabs and flakes.
Serpentinite: Metamorphic rock composed entirely of serpentine.
Slate: Metamorphic rock with distinct cleavage along planes of minerals, made from mudrocks.
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