- Granodiorite
Granodiorite (pronEng|ˌgrænəˈdaɪəraɪt/, /ˌgreɪn-) is an intrusive
igneous rock similar togranite , but contains moreplagioclase thanpotassium feldspar . It usually contains abundantbiotite mica andhornblende , giving it a darker appearance than true granite. Mica may be present in well-formed hexagonal crystals, and hornblende may appear as needle-like crystals.On average the upper continental crust has the same composition as granodiorite.
Granodiorite is a plutonic igneous rock, formed by an
intrusion of quartz-rich magma, which cools inbatholiths or stocks below the Earth's surface. It is usually only exposed at the surface aftererosion and uplift have occurred.The
Rosetta Stone was carved out of granodiorite.External links
* [http://vulcan.wr.usgs.gov/LivingWith/VolcanicPast/Notes/granodiorite.html Granodiorite definition at USGS] (public domain source)
Wikimedia Foundation. 2010.