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.
Coal gas usage may be different. Coal gas was introduced in the UK in the 1790s as an illuminating gas by the Scottish inventor William Murdoch and became very widely used for lighting, cooking, heating and powering gas engines. Coal was heated in a retort and the crude gas was passed through a condenser to remove tar and a scrubber to remove other impurities. The residue remaining in the retort was coke. The composition of coal gas varied according to the type of coal and the temperature of carbonisation. Typical figures were: In a plain burner, only the ethylene produced a luminous