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
Grammy Award for Best Rock Performance Grammy Award for Best Rock Performance The Grammy Award for Best Rock Performance is an award presented at the Grammy Awards, a ceremony that was established in 1958 and originally called the Gramophone Awards. According to the 54th Grammy Awards description guide it is designed for solo, duo/groups or collaborative (vocal or instrumental) rock recordings and is limited to singles or tracks only. This award combines the previous categories for Best Solo Rock Vocal Performance, Best Rock Performance by a Duo or Group with Vocal and Best Rock Instrumental Performance. The restructuring of these categories was a result of the