What is Xenolith?
[[Image:XenolithSierra.JPG|thumb|[[Gabbro]]ic xenolith in a granite; eastern [[Sierra Nevada (US)|Sierra Nevada]], Rock Creek Canyon, California.]] [[File:Peridotitic mantle xenolith.JPG|thumb|right|[[Peridotite]] (green) [[mantle]] xenolith in a (dark) volcanic bomb from the Vulkan-Eifel, [[Germany]]. One euro coin for scale]] A '''xenolith''' (foreign rock) is a [[rock (geology)|rock]] fragment which another rock surrounds. It happens most in [[igneous rock]] when [[magma]] is fluid enough to flow round more solid rock. Xenoliths may be covered in the margins of a [[magma]] chamber, torn loose from the walls of a flow of [[lava]] or picked up along the ground by flowing lava on Earth's surface. A '''xenocryst''' is an individual foreign [[crystal]] included within an [[igneous]] body. Examples of xenocrysts are [[quartz]] crystals in a low-[[silica]] lava and [[diamond]]s in [[kimberlite]] [[diatreme]]s.<ref>Blatt, Harvey, and Robert J. Tracy 1996. ''Petrology''. 2nd ed, W.H. Freeman. {{ISBN|0-7167-2438-3}}</ref><ref>Nixon, Peter H. 1987. ''Mantle xenoliths''. Wiley. {{ISBN|0-471-91209-3}}</ref> Although the term xenolith is most commonly associated with igneous inclusions, a broad definition could include rock fragments which have become encased in [[sedimentary rock]]. Xenoliths are sometimes found in [[meteorites]]. Xenoliths and xenocrysts provide important information about the composition of the otherwise inaccessible [[Mantle (geology)|mantle]]. [[Basalt]]s, kimberlites, [[lamproite]]s and [[lamprophyre]]s, which have their source in the upper mantle, often contain fragments and crystals assumed to be a part of the lower mantle [[mineralogy]]. == References == {{reflist}} [[File:Included fragment mcr1.jpg|thumb|left|300px|Pink [[granite]] in [[basalt]], Georgeville, [[Nova Scotia]]]] {{commons}} [[Category:Igneous rocks]]