What is Igneous rock?
[[File:Aa large.jpg|thumb|right|200px|Magma is called lava when it reaches the surface.]] [[File:Kimberlite.jpg|thumb|200px|Kimberlite (a type of crystallized igneous rock)]] [[File:Olivine basalt2.jpg|thumb|200px|Olivine basalt (a non-crystallized type of igneous rock)]] [[File:AmenhotepII-StatueHead BrooklynMuseum.png|thumb|right|200px|Head of Amenhotep II in [[granite]]. [[Brooklyn Museum]].]] '''Igneous rock''' is one of the three main rock types, the others being [[Sedimentary rock|sedimentary]] and [[metamorphic rock]]. Igneous rocks are rocks formed from molten [[magma]]. The material is made [[liquid]] by the heat inside the Earth's [[Mantle (geology)|mantle]]. When magma comes out onto the surface of the Earth, it is called [[lava]]. Lava cools down to form rocks such as [[tuff]] and [[basalt]]. [[Intrusive]] rocks are made when the magma slowly cools to form rocks under the surface. [[Granite]] is one of these. The word 'igneous' derives from the Latin word Ignis which is called fire in English. == Geological significance == The upper 16&nbsp;km (10 miles) of the Earth's [[Crust (geology)|crust]] is composed of about 95% igneous rocks with only a thin, widespread covering of [[Sedimentary rock|sedimentary]] and [[Metamorphic rock|metamorphic]] rocks.<ref>Klein, Cornelis and Cornelius S. Hurlbut, Jr. 1985. ''Manual of mineralogy,'' Wiley, 20th ed, p275 {{ISBN|0-471-80580-7}}</ref> Igneous rocks are geologically important because: * their absolute ages may be determined from various forms of [[radiometric dating]]. This gives information about the dating of adjacent non-igneous geological [[strata]]; * their features are usually characteristic of a specific tectonic environment (see [[plate tectonics]]); * in some special circumstances they host important mineral deposits ([[ore]]s): for example, [[tungsten]], [[tin]], and [[uranium]] are commonly associated with [[granite]]s and [[diorite]]s, whereas ores of [[chromium]] and [[platinum]] are commonly associated with [[gabbro]]s. === Two types =