Encyclopedia of Astrobiology

Living Edition
| Editors: Muriel Gargaud, William M. Irvine, Ricardo Amils, Henderson James Cleaves, Daniele Pinti, José Cernicharo Quintanilla, Michel Viso

Igneous Rock

  • Nicholas Arndt
Living reference work entry
DOI: https://doi.org/10.1007/978-3-642-27833-4_773-3



An igneous rock forms by solidification of magma. There are two main types: volcanic rocks that crystallize or solidify from erupted lava or fragmental (pyroclastic) material that reached the surface and contacted the atmo- or hydrosphere and plutonic or intrusive rocks that crystallize from magma that did not reach the surface. These two types are distinguished by their grain size: intrusive rocks are coarse-grained and typically show an interlocking fabric because they crystallize slowly in a thermally insulated setting, whereas volcanic rocks are fine-grained or even glassy because they cool rapidly following eruption at the Earth’s surface; crystals typically float in a fine-grained matrix. Common minerals in igneous rocks are olivine, pyroxene, amphibole, mica, feldspar, and quartz. Common intrusive rock types include peridotite, gabbro, granodiorite, and granite; their volcanic equivalents are komatiite, basalt, andesite, and rhyolite,...


Grain Size Volcanic Rock Bioorganic Chemistry Rock Type Main Type 
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Copyright information

© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  1. 1.Maison des GéosciencesLGCA, Université J. FourierSt-Martin d’HèresFrance