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. Photograph by James L. Twitter Facebook Pinterest Google Classroom. Encyclopedic Entry Vocabulary. Media Credits The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit. Media If a media asset is downloadable, a download button appears in the corner of the media viewer.
Text Text on this page is printable and can be used according to our Terms of Service. Interactives Any interactives on this page can only be played while you are visiting our website. Related Resources. View Collection. The Rock Cycle. View Article. Igneous Rocks. Sedimentary Rocks. It has been exposed to enough heat and pressure that most of the oxygen and hydrogen have been driven off, leaving a high-carbon material behind.
It has a bright, lustrous appearance and breaks with a semi-conchoidal fracture. It is often referred to as "hard coal"; however, this is a layman's term and has little to do with the hardness of the rock.
Hornfels is a fine-grained nonfoliated metamorphic rock with no specific composition. It is produced by contact metamorphism. Hornfels is a rock that was "baked" while near a heat source such as a magma chamber , sill , or dike. Marble is a non-foliated metamorphic rock that is produced from the metamorphism of limestone or dolostone. It is composed primarily of calcium carbonate. Lapis Lazuli , the famous blue gem material, is actually a metamorphic rock.
Most people are surprised to learn that, so we added it to this photo collection as a surprise. Blue rocks are rare, and we bet that it captured your eye. Novaculite is a dense, hard, fine-grained, siliceous rock that breaks with a conchoidal fracture.
It forms from sediments deposited in marine environments where organisms such as diatoms single-celled algae that secrete a hard shell composed of silicon dioxide are abundant in the water. The specimen shown above is about three inches across. Mariposite is a word that has been used in many ways. It can refer to green mica minerals, or metamorphic rocks that contain enough green mica to impart a green color.
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. Contact Metamorphism: A type of local, thermal metamorphism caused by the intrusion and extrusion of magmas; takes place in rocks at or near their contact with a body of igneous rock. Regional Metamorphism: A type of metamorphism that affects an extensive region, as opposed to local metamorphism that is effective only in a relatively restricted area.
As pressure squeezes on a parent rock during recrystallization it causes the platy or elongated minerals within the rock to become aligned, or foliated. Foliated rocks develop a platy or sheet-like structure that reflects the direction that pressure was applied in. Types of foliated metamoprhic rocks include slate, schist, and gneiss. Gneiss records the ancient beginnings of the Appalachian Mountain belt at:. Not all parent rocks have platy or elongated minerals and when these rocks undergo metamorphism the individual mineral grains do not align.
Types of non-foliated metamorphic rocks include marble, quartzite and hornfels.
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