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
Volcanic Rock (album) Volcanic Rock (album) Volcanic Rock is the second studio album by Australian proto-heavy metal band Buffalo, recorded and originally released in 1973 on the Vertigo label. The album was stylistically a much harder, heavier and rawer release than its predecessor ("Dead Forever...") – marking a move away from the band's previous progressive rock influences, although retaining a psychedelic element to their sound. "Volcanic Rock" had been recorded effectively as a live-in-the-studio effort, with only vocal and additional guitar overdubs added later during the recording sessions. The album courted controversy with its cover artwork upon its release. Illustrated by J. Phillip