Volcanic pipes are
geological structures formed by the violent,
supersonic eruption of deep-origin
volcanoes. They are considered to be a type of
diatreme. Volcanic pipes are composed of a deep, narrow cone of solidified
magma (described as "carrot-shaped"), and are usually largely composed of one of two characteristic rock types —
kimberlite or
lamproite. These rocks reflect the composition of the volcanoes' deep magma sources, where the Earth is rich in
magnesium. Volcanic pipes are relatively rare. They are well known as the primary source of
diamonds, and are mined for this purpose.