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, Iowa originally named Walters, after its first settler, but was renamed Carbon after the discovery of coal. The town was established in 1873, but was not incorporated until 1903. A post office was established in Carbon in 1874, but from 1877 to 1880, the name was changed to Shinn. By the time of the Civil War, there were small coal mines along the riverbanks near Carbon. In 1894, there were 9 coal mines in Carbon, of which 5 were in current use. Typical mine shafts were 80 feet deep, working a coal seam 12 to 20 inches (30 to 50 cm)