McAfee SECURE sites help keep you safe from identity theft, credit card fraud, spyware, spam, viruses and online scams

Home » Rocks » Metamorphic Rocks » Amphibolite

Amphibolite


A metamorphic rock composed primarily of amphibole minerals and plagioclase feldspar



What is Amphibolite?



Amphibolite is a coarse-grained metamorphic rock that is composed mainly of green, brown or black amphibole minerals and plagioclase feldspar. The amphiboles are usually members of the hornblende group. It can also contain minor amounts of other metamorphic minerals such as: biotite, epidote, garnet, wollastonite, andalusite, staurolite, kyanite and silimanite. Quartz, magnetite and calcite can also be present in small amounts.


How Does Amphibolite Form?



Amphibolite is a rock of convergent plate boundaries where heat and pressure cause regional metamorphism. It can be produced through the metamorphism of mafic igneous rocks such as basalt and gabbro or from the metamorphism of clay-rich sedimentary rocks such as marl or graywacke. The metamorphism sometimes flattens and elongates the mineral grains to produce a schistose texture.


Uses of Amphibolite



Amphibolite has a variety of uses in the construction industry. It is harder than limestone and heavier than granite. These properties make it desirable for certain uses. Amphibolite is quarried and crushed for use as a aggregate in highway construction and as a ballast stone in railroad construction. It is also quarried and cut for use as a dimension stone.

Higher quality stone is quarried, cut and polished for architectural use. It is used as facing stone on the exterior of buildings, and, as floor tile and panels indoors. Some of the most attractive pieces are cut for use as countertops. In these architectural uses amphibolite is one of the many types of stone sold as "black granite".

Some amphibolite deposits, such as the one at Gore Mountain, in the Adirondacks of New York, contain significant amounts of garnet. If enough garnet is present and of proper quality the amphibolite can be mined and the garnet recovered for use as an abrasive.


More Metamorphic Rocks
  Schist
  Slate
  Soapstone
  Quartzite
  Novaculite
  Gneiss
  Marble
  Amphibolite



Find it on Geology.com




More from Geology.com


US Diamond Mines
US Diamond Mines: Did you know that diamonds can be found in the United States?
Download Google Earth Free
Free Google Earth software allows you to browse seamless world satellite images. Free.
volcanic explosivity index
Volcanic Explosivity: Learn about some of the most explosive volcanic eruptions.
Gems from Space
Gems from Space A number of materials from space have been used as attractive gems.
shale gas
Shale Gas is natural gas trapped within shale. It is a growing source of US supply.
Plate Tectoncs
Zoom in on Plate Boundaries: See the details of plate tectonics in satellite view.
Novarupta
Wrong Volcano! The most powerful eruption of the 20th century was misidentified?
Labradorite
Labradorite: A feldspar that produces bright flashes of iridescent colors.


Amphibolite
Amphibolite is a coarse-grained metamorphic rock that has amphibole minerals such as the hornblende group as its primary ingredient. The specimen shown is about two inches (five centimeters) across.




Amphibolite
Some amphibolites are greenish as determined by the color of the amphibole minerals. This specimen is actually an igneous rock. Some geologists call an igneous rock composed primarily of amphibole minerals an amphibolite or "hornblendite". USGS image.


Marcellus Shale
Mount Rainier Volcanic Hazards
Blood Diamonds
Largest Eruption of the 20th Century
Rare Earth Elements
Rock Type Photo Gallery
What is a Debris Flow?
Who Owns The Arctic?


© 2005-2014 Geology.com. All Rights Reserved.
Images, code and content of this website are property of Geology.com. Use without permission is prohibited. Pages on this site are protected by Copyscape.