Kimberlite Kimberlite Kimberlite is an igneous rock, which sometimes contains diamonds. It is named after the town of Kimberley in South Africa, where the discovery of an diamond called the Star of South Africa in 1869 spawned a diamond rush and the digging 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 in vertical structures known as kimberlite pipes, as well as igneous dykes. Kimberlite also occurs as horizontal sills. Kimberlite pipes are the most important
Volcanic rock of most volcanic rocks tends to increase the silica (SiO) content, mainly by crystal fractionation. The initial composition of most volcanic rocks is basaltic, albeit small differences in initial compositions may result in multiple differentiation series. The most common of these series are tholeiitic, calc-alkaline, and alkaline. Most volcanic rocks share a number of common minerals. Differentiation of volcanic rocks tends to increase the silica (SiO) content mainly by fractional crystallization. Thus, more evolved volcanic rocks tend to be richer in minerals with a higher amount of silica such as phyllo and tectosilicates including the feldspars, quartz polymorphs and muscovite.