Kimberlite

Kimberlite is a rare, volatile-rich, ultramafic igneous rock best known for being the primary source of diamonds. It forms deep within the Earth's mantle, typically at depths of 150–450 km, where high pressure and temperature conditions allow diamonds to crystallize. Kimberlite magmas originate in these deep mantle regions and erupt rapidly and explosively through the Earth's crust, carrying diamonds and other mantle-derived minerals to the surface. These eruptions create carrot-shaped pipes, known as kimberlite pipes, which are the world's most significant sources of gem-quality diamonds. Kimberlite is composed of a mixture of olivine, phlogopite, pyroxene, carbonate minerals, and serpentine, often containing mantle xenoliths (foreign rock fragments) that provide valuable insights into the Earth's deep interior. The presence of CO₂ and H₂O in kimberlite magmas contributes to their explosive eruption style, which is unlike typical volcanic eruptions. The rapid ascent of kimberlite magma is crucial for preserving diamonds; if the magma rose more slowly, the high temperatures and pressures could cause the diamonds to transform into graphite. Kimberlite deposits are found in stable continental cratons, regions of ancient, thick lithosphere that provide the necessary conditions for diamond formation. Major kimberlite fields are located in South Africa, Russia, Canada, Australia, and Brazil. The famous Kimberley region in South Africa, where kimberlite was first identified, played a crucial role in the global diamond industry. In addition to diamonds, kimberlites contain various trace minerals, such as garnet, ilmenite, and chromite, which help geologists identify potential diamond-bearing deposits. However, not all kimberlite pipes contain economically viable diamonds, and extensive exploration is required to determine their commercial value. Beyond its economic significance, kimberlite is scientifically important because it brings deep-mantle materials to the surface, providing clues about the Earth's composition, mantle dynamics, and the conditions under which diamonds form.