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
Coso Rock Art District Coso Rock Art District Coso Rock Art District, containing the Big and Little Petroglyph Canyons, is a rock art site containing over 100,000 Paleo-Indian and/or Native American Petroglyphs. The Coso Range is between the Sierra Nevada and the Argus Range. Indian Wells Valley lies to the south of this location. This north-south trending range of about consists of rhyolitic domes and outcrops of volcanic rock. Also known as Little Petroglyph Canyon and Sand Tanks, Renegade Canyon is but one of several major canyons in the Coso Range, each hosting thousands of petroglyphs (other locations include Haiwee Springs, Dead End Canyon,