Volcanic pipe Volcanic pipe Volcanic pipes are subterranean 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. Volcanic pipes form as
Lake Ellen Kimberlite till. Magnetic survey work done in 1956 depicts an elliptical positive anomaly long in an east–west direction and wide, which probably defines the limits of the pipe. The kimberlite is intruded into volcanic rocks of the Proterozoic Hemlock Formation. The exposed material is grayish green to reddish, iron stained highly weathered and consists of disaggregated rubbly fragments up to . It is generally accepted that the pipe was emplaced about 180 million years ago. The lake Ellen Kimberlite is popular with rock hounds as the classic indicator minerals (pyrope, magnesian ilmenite and chrome diopside) for kimberlite are easily found in