Kimberlite

Kimberlite is an igneous rock best known for sometimes containing diamonds. It is named after the town of Kimberley in South Africa. The discovery of a big diamond in 1871 started a "diamond rush". This resulted in the Big Hole, a large open mine.
Kimberlite occurs in the Earth's crust in vertical structures known as "pipes" as well as igneous dykes and sills. Kimberlite pipes are the most important source of mined diamonds today. Kimberlites form deep with the Earth's mantle. Formation occurs at depths between Kimberlite material is erupted rapidly and violently, often with considerable carbon dioxide and other volatile components. 
Kimberlite has attracted attention because it serves as a carrier of diamonds and garnet peridotite mantle xenoliths to the Earth's surface. The study of kimberlite has the potential to provide information about the composition of the lower mantle. Little is known about melting processes at or near the interface between the cratonic continental lithosphere and the underlying convecting asthenospheric mantle.