The Element Carbon on Earth

The element carbon is widely distributed in nature. l It is found in the earth s crust in the ratio of 180 ppm, most of it in the form of compounds. l Many of these natural compounds are essential to the production of synthetic carbon materials and include various coals (bituminous and anthracite), hydrocarbons complexes (petroleum, tar, and asphalQ and the gaseous hydrocarbons (methane and others). 

Only two polymorphs of carbon are found on earth as minerals natural graphite (reviewed in Ch. 10) and diamond (reviewed in Chs. 11 and 12). 

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