Carbon the very large masses of carbonate rock (limestone, dolomite, marble and so on). Coal is very rich in carbon (anthracite contains 92–98%) and is the largest commercial source of mineral carbon, accounting for 4,000 gigatonnes or 80% of fossil fuel. As for individual carbon allotropes, graphite is found in large quantities in the United States (mostly in New York and Texas), Russia, Mexico, Greenland, and India. Natural diamonds occur in the rock kimberlite, found in ancient volcanic "necks", or "pipes". Most diamond deposits are in Africa, notably in South Africa, Namibia, Botswana, the Republic of the Congo, and Sierra Leone.
Carbon planet Carbon planet A carbon planet is a theoretical type of planet that contains more carbon ("Z" = 6) than oxygen ("Z" = 8). Carbon is the fourth most abundant element in the universe by mass after hydrogen, helium, and oxygen. Marc Kuchner and Sara Seager coined the term "carbon planet" in 2005 and investigated such planets following the suggestion of Katharina Lodders that Jupiter formed from a carbon-rich core. Prior investigations of planets with high carbon-to-oxygen ratios include Fegley & Cameron 1987. Carbon planets could form if protoplanetary discs are carbon-rich and oxygen-poor. They would develop differently from Earth, Mars,