Editing Kimberlite (section)

{{short description|Igneous rock which sometimes contains diamonds}}
{{Infobox rock
|name = Kimberlite
|type = Igneous
|image = Kimberlite (Hamilton Branch Kimberlite, Elliott County Peridotite, Late Cretaceous, ~75 Ma; between Ison Creek & Hamilton Branch, Elliott County, Kentucky, USA).jpg
|caption = Kimberlite from the United States
|composition =  Forsteritic olivine and carbonate minerals, with trace amounts of magnesian ilmenite, chromium pyrope, almandine-pyrope, chromium diopside, phlogopite, enstatite and titanium-poor chromite. Sometimes contains [[diamond]]s.
}}
[[Image:Kimberlite crosssection QEMSCAN.png|thumb|False-color [[scanning electron microscope]] image of kimberlite from South Africa. [[Olivine]] crystals (green) are in a fine-grained [[Matrix (geology)|matrix]] made up of clay minerals and carbonates (presented in blue, purple and [[Buff (color)|buff]] colors).]]

'''Kimberlite''' is an [[igneous rock]] and a rare variant of [[peridotite]]. It is most commonly known as the main host matrix for [[diamond]]s. It is named after the town of [[Kimberley, Northern Cape|Kimberley]] in [[South Africa]], where the discovery of an 83.5-[[Carat (mass)|carat]] (16.70 g) diamond called the [[Star of South Africa (diamond)|Star of South Africa]] in 1869 spawned a [[diamond rush]] and led to the excavation of the [[open-pit]] mine called the [[Big Hole]]. Previously, the term kimberlite has been applied to olivine lamproites as Kimberlite II, however this has been in error.

Kimberlite occurs in the Earth's [[Crust (geology)|crust]] in vertical structures known as [[Volcanic pipe|kimberlite pipes]], as well as igneous [[Dike (geology)|dykes]] and can also occur as horizontal [[Sill (geology)|sills]]. Kimberlite pipes are the most important source of mined diamonds today. The consensus on kimberlites is that they are formed deep within [[Earth's mantle]]. Formation occurs at depths between 150 and 450 kilometres (93 and 280&nbsp;mi), potentially from anomalously enriched exotic mantle compositions, and they are erupted rapidly and violently, often with considerable [[carbon dioxide]] and other [[Volatile (astrogeology)|volatile]] components. It is this depth of melting and generation that makes kimberlites prone to hosting diamond [[xenocryst]]s.

Despite its relative rarity, kimberlite has attracted attention because it serves as a carrier of diamonds and [[garnet]] peridotite mantle [[xenolith]]s to the Earth's surface. Its probable derivation from depths greater than any other [[igneous rock]] type, and the extreme [[magma]] composition that it reflects in terms of low [[silica]] content and high levels of [[incompatible element|incompatible]] [[trace-element]] enrichment, make an understanding of kimberlite [[petrogenesis]] important. In this regard, the study of kimberlite has the potential to provide information about the composition of the deep mantle and melting processes occurring at or near the interface between the [[craton]]ic continental [[lithosphere]] and the underlying convecting [[asthenosphere|asthenospheric]] mantle.