Ultramafic rock but there are ultrapotassic and highly silica-under-saturated rocks with >18% MgO which can be considered "ultramafic". Ultrapotassic, ultramafic igneous rocks such as lamprophyre, lamproite and kimberlite are known to have reached the surface of the Earth. Although no modern eruptions have been observed, analogues are preserved. Most of these rocks occur as dikes, diatremes, lopoliths or laccoliths, and very rarely, intrusions. Most kimberlite and lamproite occurrences occur as volcanic and subvolcanic diatremes and maars; lavas are virtually unknown. Vents of Proterozoic lamproite (Argyle diamond mine), and Cenozoic lamproite (Gaussberg, Antarctica) are known, as are vents of Devonian lamprophyre (Scotland). Kimberlite
Kimberlite (lower amounts of HO) in the system, which produces a deep explosive boiling stage that causes a significant amount of vertical flaring. Kimberlite classification is based on the recognition of differing rock facies. These differing facies are associated with a particular style of magmatic activity, namely crater, diatreme and hypabyssal rocks. The morphology of kimberlite pipes and their classical carrot shape is the result of explosive diatreme volcanism from very deep mantle-derived sources. These volcanic explosions produce vertical columns of rock that rise from deep magma reservoirs. The morphology of kimberlite pipes is varied, but includes a sheeted dyke complex