Download digital geologic maps for entire states Where can I find information about the geology and natural history of National Parks? Our National Parks are the showcases of our nation's geological heritage.
The National Park Service has websites for most individual parks that include information about their geology and natural history. The website has listings for regions of the country What is the difference between a rock and a mineral?
A mineral is a naturally occurring inorganic element or compound having an orderly internal structure and characteristic chemical composition, crystal form, and physical properties. Common minerals include quartz, feldspar, mica, amphibole, olivine, and calcite.
A rock is an aggregate of one or more minerals, or a body of undifferentiated mineral What are igneous rocks? Igneous rocks from the Latin word for fire form when hot, molten rock crystallizes and solidifies. The melt originates deep within the Earth near active plate boundaries or hot spots, then rises toward the surface.
Igneous rocks are divided into two groups, intrusive or extrusive, depending upon where the molten rock solidifies. Filter Total Items: 4. Year Published: Famous building stones of our Nation's capital The buildings of our Nation's Capital are constructed with rocks from quarries located throughout the United States and many distant lands.
View Citation. Famous building stones of our Nation's capital; ; FS; ; U. Geological Survey. Year Published: Building stones of our nation's capital Withington, C. Filter Total Items: 2. Date published: April 4, Date published: October 4, Filter Total Items: 6. List Grid. March 23, July 20, March 14, Attribution: Mineral Resources Program.
September 19, August 30, A metamorphic rock , on the other hand, began as a rock—either a sedimentary, igneous, or even a different sort of metamorphic rock. Then, due to various conditions within the Earth, the existing rock was changed into a new kind of metamorphic rock.
The conditions required to form a metamorphic rock are very specific. The existing rock must be exposed to high heat, high pressure, or to a hot, mineral-rich fluid. Usually, all three of these circumstances are met. In order to create metamorphic rock, it is vital that the existing rock remain solid and not melt. If there is too much heat or pressure, the rock will melt and become magma.
This will result in the formation of an igneous rock , not a metamorphic rock. Consider how granite changes form. Granite is an igneous rock that forms when magma cools relatively slowly underground.
It is usually composed primarily of the minerals quartz, feldspar, and mica. When granite is subjected to intense heat and pressure, it changes into a metamorphic rock called gneiss. Slate is another common metamorphic rock that forms from shale. Limestone, a sedimentary rock , will change into the metamorphic rock marble if the right conditions are met. This happens due to geologic uplift and the erosion of the rock and soil above them.
At the surface, metamorphic rocks will be exposed to weathering processes and may break down into sediment. These sediments could then be compressed to form sedimentary rocks, which would start the entire cycle anew. Any rock type can become any other. 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.
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. 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. These properties make it useful for a wide variety of architectural, practical, and artistic uses. Slate is a foliated metamorphic rock that is formed through the metamorphism of shale. It is a low-grade metamorphic rock that splits into thin pieces.
The best way to learn about rocks is to have a collection of specimens to examine while you study.
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