This change happens without any melting of the rock. Everything remains solid while the metamorphism occurs. We know from experiments that certain minerals form only at very specific temperatures and pressures.
If we find a rock that has minerals such as a diamond that only form at high pressures, we know that it must have formed deep in the Earth.
Something must have happened to bring the rock up to the surface where we could find it. For information on user permissions, please read our Terms of Service. If you have questions about how to cite anything on our website in your project or classroom presentation, please contact your teacher.
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Text on this page is printable and can be used according to our Terms of Service. Any interactives on this page can only be played while you are visiting our website. You cannot download interactives. Igneous rocks are one of three main types of rocks along with sedimentary and metamorphic , and they include both intrusive and extrusive rocks.
Sedimentary rocks are one of three main types of rocks, along with igneous and metamorphic. Join our community of educators and receive the latest information on National Geographic's resources for you and your students. Skip to content. Image Metamorphic Rock Isua Metamorphic rock, estimated to be as old as 3. Gold prospectors learned that gold could be found in areas where these green rocks were present.
This is because mariposite is an ore of gold. Quartzite is a non-foliated metamorphic rock that is produced by the metamorphism of sandstone. It is composed primarily of quartz. The specimen above is about two inches five centimeters across. Phyllite is a foliated metamorphic rock that is made up mainly of very fine-grained mica.
The surface of phyllite is typically lustrous and sometimes wrinkled. It is intermediate in grade between slate and schist. Skarn is a rock characterized by its formation rather than its mineral composition.
It often forms when carbonate rocks near a magma body are altered by contact metamorphism and metasomatism. Various minerals, gems , and even precious metals can sometimes be found in skarn. Schist is a metamorphic rock with well-developed foliation. It often contains significant amounts of mica which allow the rock to split into thin pieces. It is a rock of intermediate metamorphic grade between phyllite and gneiss.
The specimen shown above is a "chlorite schist" because it contains a significant amount of chlorite. It is about two inches five centimeters across. Soapstone is a metamorphic rock that consists primarily of talc with varying amounts of other minerals such as micas, chlorite , amphiboles, pyroxenes , and carbonates.
It is a soft, dense, heat-resistant rock that has a high specific heat capacity. Notice the platy layers that run from left to right within the rock.
It looks as though you could easily break off layers from the front surface of the outcrop. This layering is a result of the process of metamorphism. Metamorphism is the changing of rocks by heat and pressure. They change so much that they become an entirely new rock.
Metamorphic rocks start off as igneous, sedimentary, or other metamorphic rocks. One ways rocks may change during metamorphism is by rearrangement of their mineral crystals. When heat and pressure change the environment of a rock, the crystals may respond by rearranging their structure.
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