Volcanic pipe
Volcanic pipes or volcanic conduits are subterranean geological structures formed by the violent, supersonic eruption of deep-origin volcanoes. They are a type of diatreme composed of a deep, narrow carrot-shaped cone of solidified magma usually composed of kimberlite or lamproite. These rocks reflect the composition of the volcanoes' deep magma sources rich in magnesium. They are the primary source of diamonds and are mined for this purpose. While diatremes are common, being the second commonest form of magma extrusion reaching the surface, volcanic pipes are relatively rare.